i just bought an older Greddy SP1 exhaust. the muffler ovalular part and tip are stainless steel, but it's so, so dirty. i can see a nice piece under all the grime. but stainless steel can be very picky. so how do i go about cleaning it? man is it dirty!

 

I've had sucess with Flitz on pretty much every metal I've used it on. Also, Mother's Mag and Aluminum polish is my go to on every metal, not just what they advertise for.

 

I've also had good luck with Mother's Mag...

 

Also check out these guys:

http://www.jet-hot.com/

Won't stop carbon build up, but will make heat discoloration a thing of the past...

 

you could also use pickling gel from a welding specialist, it's so remove the blackness from the weld for stainless steal