I was wondering if those stainless steel pipes from Ace Hardware could be used as a test pipe(removeing cat and welding the pipe where the cat was) I have 2 headerback exhausts right now, and one of the cat is clogged. So yeah, could I weld on a stainless steel pipe from ace hardware.

 

I made one out of aluminized steel by cutting the cat off too. It never rusted since I sprayed the entire down pipe with a high heat paint (1200F)

 

if you can weld the stainless, sure. It will be louder, And if your in an emissions testing state, you probably won't pass.