Done quite a bit of searching on this subject buy couldnt find any occurances without test pipes. The Z is making a really annoying rattle/buzz/raspy noise when I hit 2500 and 3300 rpms. The noise will only last for about 100 rpm's and only when the car is in second gear or higher - the noise will not occur in neutral or in first gear. I do have a Nismo exhaust which has scraped a few times due to the car being lowered. Nissan of course says that the noise is comming from my "aftermarket suspension" - obviously this is not the case. Any ideas?

 

The flex sections on the Nismo will do that under pressure with tp's, mine did it with hfc's.

 

I can say that my 06 dash rattles at certain speeds because my BFG tires are so loud.

 

Thanks for the replies and sorry for the confusion - I have the stock cats, thats why its just not making any sense to me.

 

i was gonna say itd be your test pipes, but seeing as you dont have those... theres a ground cable that goes to the rear muffler. when i had my stock one on, it made a weird noise when i revved it. but i took it off and no more noise. the only rasp i got was from tp's.

 

I can also detect a smell exiting the driver's side - almost smells similar to a new exhaust system.