i just installed a header and i have a cat back and a test pipe so no cats, well when i drive and hit about 3k rpm it makes the most awful rattling raspy sound ive ever heard. my cat back its the n1 style off ebay , could it be a baffel inside the muffler making the sound or is it just from the header, ive had header back exh. and no cats on many other cars and they never made this sound, sounds like a beat up old honda, i dont even want to drive it sounding like this

 

Nice name swap headers and check that would probably tell u where the problem lies

 

This is a very common issue that many people with a header and cat-backs have.

I am running a OBX header/mid-pipe and MagnaFlow catback.
I am too cattless and had this issue.
Just found the cure a few weeks ago and will do a write-up soon.

But it is a exhaust leak that only shows it's ugly face at about 3k rpm's and above.
It's either in your header gasket or one of your flang gaskets.
I would call Speed Corps and order a 4G94 exhaust manifold gasket and get thick FelPro flang gaskets.
Replace these and you should be good.

 

awsome thanks, i hope it works, i did reuse one old gasket too so im hoping thats it

 

Put a high flow cat on, had the EXACT same problem on my 05 RA.

 

What flange gaskets did you use?
replacing my crappy ones fixed my issue.

 

yeah my car sounds like this from about 2500-3500 rpm. but not really above.... im assuming its the same problem...

 

Exhaust leaks u cant normally hear that loud inside the vehicle. But from what i had issues with was with the brackets.. They would come off, or the whole system would be moved slightly and would rub against the the suspension somewhere, and it would make alot of noise, resembling exhaust noise because it was harmonic with the rpm.. very annoying, and very loud inside the car, and outside also.

If u want to replace ur gaskets, u can look into getting some gasket cloth (may not be the right term) and cutting the gaskets out by hand to make some good gasket making materal.. copper seal and those aluminum looking pin hole 'paper' gaskets that come with the kits are garbage.