I've seen several reviews of cats, and if I rehash things others have said, my apologies. I just want to relate my personal experience.

My wife got me a set of used kinetix cats for me as an early anniversary present(great wife, huh?). I had not been interested in cats at all, until it last week. I was discussing my desire to get a small v8-like exhaust gurgle, like on mustangs. It was suggested to me to get some crawford highflows, and a stillen gen1 sedan exhaust. I promptly found myself in the market for new cats. Thus the new kinetix(used, much cheaper than I could have obtained the crawfords).

I installed them myself at a relative's shop. He has all the tools, and it's a big convenience. I just with he had a lift; it's a boat shop, so he had no need. Anyway, other than doing the ztube/k&n and the coupe shocks/springs, I have *never* wrenched on a car before. The install took me about 5 hours underneath the car on jackstands(that's total time, including cool-down from the drive over to the shop). It would have been much shorter, but I have an acute lack of upper body strength and had to have help breaking loose several of the bolts on the stock cats.

The only major pain in replacing the cats was reaching the upper two bolts where the cats attach to the stock headers. There wasn't enough room to get any kind of tool up there, so we had to go through the engine compartment, with multiple extensions, to reach them. When everything was loose, I dropped the stock cats without any problems. The O2 sensors fit just fine, and the kinetix had visually-perfect fitment. The only thing that concerned me was the brace that connected to the stock cats couldn't be bolted to the kinetix.

We got the car off the jacks, cranked it up, and it sounded pretty good. So I left his shop, and promptly noticed a distinct(read LOUD) rattle coming from the driver's-side cat. I drove it home, because from what I had read before the install, I just assumed it was the heatshield.

The next day, I took it to a local oil-change place. We got in the pit and took off the heat shields. When I left, the rattle was still there. It was so bad, that had someone gotten in my car that had not known about the mod, he would have thought something was broken.

The next day(yesterday) I took it to a muffler shop to see if they could fabricate an extension to the stock brace to help support the new cats. Unfortunately, they could not. They did, however, use a hammer and crowbar to bend back the sheetmetal in the upper cat cavity. I cringed, but when I inspected it, there was very little evidence of the work. I took it for a test drive, and they had elimenated the rattle completely.

Until my ride home from work yesterday. When I was at the muffler shop, I had them reinstall the heat shields. The left cat is now rattling against its heat shield(completely different rattling sound from before). I now have to have it removed, again.

So, the entire experience has been a pain. But now that the major rattles have been accounted for, I can actually hear the cats. They sound absolutely fabulous. Fortunately, there has been little rasp. What rasp I have experienced has been random, and very short. Sound under load, at 3k is great. At 5k, WOT, it's crazy. From 2 to 3k, it's got a distinctive euro flavor.

The only other exhaust mod I have is a 350z middy. Still have the stock ypipe and muffler. Overall, this is a great combination. Now I just have to save up for a full cat-back.

Does anyone know if hks makes a sedan variant of it's coupe exhaust?

It's really disappointing that shops like Crawford, Kintex, etc automatically assume things like OEM exhaust supports are not needed. The cat support is needed to:

1) OFFER SUPPORT FOR THE ENTIRE WEIGHT OF THE EXHAUST!!!

2) To keep things from torquing and moving under load.

We had these sorts of problems with the Maxima and exhaust systems. Lots of aftermarket companies figured that not using one or two exhaust supports would by "fine". Little do they realize...or care that not using these supports create rattles, buzzes, and vibrations.

Another thing to consider is that the rattles you're experiencing are most likely being picked up by the knock sensor therefore reducing your power.

As for catbacks, I too have been looking around. I'm actually considering the Borla TD setup. I don't plan on messing with the cats.

I had not considered the knock sensor issue. When it was first installed, I thought that I might have noticed a small increase at WOT, say in 2nd at 4k. But that was immediately after the install. I figured that I was imagining it, or was trying to justify lying on my back on concrete for a few hours.

However, I have since driven around 150 miles, and now I think I might have lost a little punch. Either way, the gain or loss is too little to really matter. After all, I was really after the sound, not worried much about performance. On the other hand, if I lose a tenth or two in the 1/4, those bad boys are coming off!

As for the type of catback exhaust system to get, we might want to move this to another thread, but I've decided to stay away from the borla. First, at least on the coupes, it doesn't offer the same performance as the Stillen(don't know how that translates to the sedan versions of said exhausts; maybe not at all). Additionally, and please correct me if I'm wrong, but the borla comes in a thousand pieces. And although most people haven't had problems, there have been several that have problems with the seals and exhaust leaks. Believe me, if anyone's going to experience a problem with a kit, I will.

From what I've been able to gather, the workmanship on the stillen is top-notch, and it's a direct bolt-up. JBX has commented on this.

Zimbo had/still has(haven't checked lately) a Stillen gen1 sedan exhaust. He says he'll take $450, shipped. It was cut for removal, but that shouldn't be a big deal for any muffler shop. I'm strongly considering it. The only reason I haven't bought it yet is that I am waiting for this new revup motordyne mod, and I will also be needing tires soon(only have 9k on my stock goodyears).

I've searched around and I haven't seen much definitive proof the Stillen or the Borla is any better one another. They've got the same exact layout thereofre I'd think they both would produce the same types of numbers. The dynos I've seen seem to support that.

As for rattles and exhaust leaks, the Borla does come in a few more pieces, but it's been my past experience with F-bodies and Stangs that Borla makes a quality peice and they usually use a fairly decent gauge metal to quell rasp. The setup is about $300 cheaper too. You do have to know what you're doing and be patient when doing the installation. Do it wrong, and you will gets leaks and rattles. The clamps they use are off a very high quality and reduce the potential for leaks, but people fail to realize that you do need to tighten them after the exhaust has heat cycled a couple times. I have a hard time giving Stillen any of my money because I've never had good luck with they're exhaust products. They've been cheap, had nasty welds, and the quality of metal was thin and the low grade stainless would rust.

Surprised to hear you lost power Trey. The Higher flow cats should respond perhaps after some time when the ecu can adapt. I would not expect a loss but maybe the 05's need the backpressure more than previous years.

I don't know if I have in fact gained, or lost, anything. I haven't dynod, and I'm not sure I plan on dyno'ing again for various reasons. Any impressions that I have so far are purely subjective, hence limited to my perception. While I consider myself an audiophile, and can hear even the smallest change, I honestly don't think I can *feel* a few hp.

In the end, I'm not sure I really care about the performance impacts. The sound is just SOOOO pleasing. In fact, I have some admittedly crappy recordings taken from my pda/phone. The mic was too close to the source, so it was overly muffled. And they're wavs, so I'm having a hard time converting to mp3 with the tools I presently have, to compress them. Once I clean them up a bit, I'll post them on this thread.

Nothing cheap 'bout anything on this system. Had Borla on my SC'd 02' Avalanche. Nice too, as you said.......many pieces and I also had major fitment issues. The 'final solution' was that I went to Corsa and never looked back. As far as my Stillen gen II CB goes...luv it and feel it was a worthwhile mod. UBC, jbx

outta sequence, but you get the idea........