^^ Like Gary C said, it all depends on the laws of which state you live in. I live in Cali, and was actually thinking of running a test pipe, but do not want to go through the hassle. This is why most of the parts I put on are carb approved or somewhat legal in CA... Just go with an HFC and you will get the sound and moderate gain in power. After installing the Kinetix HFC I can feel the car pull harder right around 3500rpm+....

 

I have Berk HFC and I love the sound. On startup its very bassy and rumbles yet amplifies the stock exhaust note. I felt noticeable power gains even after I had put my MREV2 and spacers on. You can't really go wrong with Berk HFC. So much lighter than your original catalytic converters. Look into Fast Intentions HFC, they're really good quality. Someone had mention about the CEL light being turned on after install. I was easily able to remove the light with an ECU reset. The only drawback with HFC is going to CA emissions. One negative thing I can point out is you can hear a hissing noise when depressing on the gas pedal which could be heard even with windows rolled up.

 

I would get some Berk HFC's. Keep looking at the marketplace, there are usually some good deals. I got mine brand new from a vendor for $380 last lyear.

 

If I install Berk HFCs on my stock exhaust system will I still have a chance of failing emissions. Also do HFC enhance droning in the exhaust system or is that mostly the muffler?

 

I've had my CHECK ENGINE SOON light come on several times since I installed my BERKS HFCs. The cause is I'm running a little lien due to the combination of my intake, exhaust and hfcs. This warning comes and goes, I need to do a tune and gain a few more needed HP....
Gary

 

I picked up a set of used Fast Intentions HFC's in the market place for $280 shipped I believe. I'm very happy with them, and I was actually a little surprised by the gains I felt. I did install an HR y pipe at the same time.

They sound really nice, but there is a slight kind of rattle sound at WOT in the higher RPM range. I don't know if this is rasp or what...

 

I've put off getting HFC's because I heard they don't last long... like 2 years and then you need new ones (to pass emissions). Any truth to this? If I thought they would last 4+ years I'd definitely do it.

 

I did a bunch of research before buying my HFCs and found that "most" people do not exp any issues with a code being thrown with their HFCs.
Especially not Berk.
That being said there's always exceptions of course...
I also contacted about 6 members on this site to see if they had probs passing smog with their HFCs and they didn't.
I finally took the dive a couple months ago and have been very happy with my Berks.
I wish my setup had a deeper growl but thats a matter of changing my exhaust,
which I don't think I'll be doing any time soon.