Currenly have a 2011 g37xs. Stillen headers, FI test pipes, ISR Y pipe and Stillen mid pipe+ muffler. I hear rasp at around 3k rpm and also hear a rattle while driving at 1.5k rpm (cant hear the rattle when revving still) I Need suggestions on what to do to clear both that rattle and the rasp. Muffler shop couldnt figure out the rattle since the heat shield seems to be tightened, was thinking of adding a hanger at the test pipe because maybe its rattling and hitting the heat shield? as for the rasp I was thinking of changing up the muffler to a resonated axle back to elimiate rasp. Also heard of changing from test pipes to HFC but im unsure of what to do at this point. Any help is greatly appreciated, thanks!

 

From my research the rattle comes from the flex sections on the Ypipe. I get it at about 2.9 to 3k. The solution is to heat wrap the flex sections. I have yet to try this though. I dont really have rasp that much. I have megan test pipes resonated, ebay Y, stock mid and stock muffler. Maybe you could put your stock mid pipe back on there and see what happens.

 

Need resonators installed as close to the test pipes as you can get them to kill the rasp. Vibrant has a good selection or you can go with the magnaflow resonated X pipe insert. Do you still have the mid chassis brace on the underside of the car? Would be the piece of metal under the car that runs perpendicular to the exhaust, right where the Y pipe and mid pipe flanges meet; give or take 5 inches. Check to see if the exhaust is resting on this; or the clearance might only be a few 16ths of an inch. I had the exact same issue when I installed my test pipes. The absence of the hanger on the aftermarket test pipes allows the exhaust to flex/sag when in drive and that's where the rattle was coming from.

If that isn't the source, take a look at the clearance of your exhaust to your rear sway bar.