Hi all, I hope that this is the appropriate forum for this sort of post. I've scoured the forums for my options on this very common problem and at this point am just looking for opinions!

I've got an 07 g35s sedan. I have beluga resonated test pipes, motor dyne XYZ pipe with resonator module, and I just added a custom 3inch y to dual 2.5 all the way back with small magna flow bullet style mufflers in place of the resonators. Before adding the custom 2.5 back, there was no rasp to speak of. However, after changing out the mid pipe (and replacing the stock resonators with the magna flow) I have absolutely deplorable rasp. Huge mistake, I know, I'm pretty stupid sometimes, test pipes and no resonators is a huge mistake. The car is completely un drivable for my standards. There are now 2 rasp zones, one that occurs from 2000-2100 and another from 3200-4k..

I've done a bunch of research about this problem, and I am exploring a couple of options.

1) Put the stock cats back on
2) Get rid of the motor dyne y pipe and add a custom true dual setup with the Magnaflow x pipe muffler that seems to solve most rasp problems. (Willing to sell my lightly used Motordyne Y pipe on here if I choose this option. Willing to ship!)
3) Add two big mufflers at the back of the current setup, or 20in resonators somewhere.

Does anyone have any thoughts about these options? Would putting the stock cats on completely get rid of the rasp? I like the sound clips of true dual setups with the x pipe muffler, but am worried I might have different results considering I have the sedan and a custom exhaust.. Thoughts? Thanks, I hope everyone isn't too tired of reading peoples rasp horror stories, but I made the mistake and I just need some input on how to move forward from here.

 

Try swapping the OEM cats back on and see what the result is before you do anything else. If you can DIY it won't cost any money, just some of your time. If that doesn't solve your issue then go from there with other options.

 

Sorry I don't have any help for you except price shipped to 46628?

 

Welcome to G35 Driver, dcram! Your OE exhaust system is over-whelmed by the extra volume created by replacing those restrictive OE cats. Put the factory cats back on and see what results you get.
Gary

 

Replaced the test pipes with stock cats and it smoothed everything out nicely. Pure VQ goodness out of the exhaust now . Only thing is I now have a really obnoxious knocking/vibration from the right cat when the car is cold. After about 1 minute of driving it goes away though.. I'll try to investigate the heatsheilds and see if can find the rattle. Thanks for the replies!