cat convertos
 

I have 01 gt thinking of removing the cats,leaving the mini cats on,then installing performance mufflers ( flowmasters or dynomax)question , would there be any hp gain by removing the cats and would it be to loud without the cats,or would it be better to leave the cats and install just the mufflers.

yeah, no cats = loudness. i have an offroad h-pipe and 40 series flowmasters (the loudest ones...2 chamber) and it's very loud. i had a state trooper following me around yesterday afternoon with his window down. i was like baaaaarely touching the gas to get home :)

you'll see an increase in hp with no cats since you're opening up the exhaust more. in my opinion, if you're gonna remove cats, remove them ALL, or none.

I prefer the sound and performance of the Dynomax Ultra-flo. The Flowmaster (435cfm) is louder than the Dynomax (1135cfm). Since the engine is nothing more than an air pump, logic told me to use the Dynomax Ultra-flo welded system for greater air movement.
I would also do more homework on the "H", "X", or "pro-chamber" systems. I've heard the Mac is a great system, also X-pipes, but I've heard the H-pipe is an older theory. So take your time and investigate further.