What are the quietest hi flow cats on the market?

 

all the hi-flows have relatively the same volume increase

 

Random Technology's cat keeps your emissions the same and (from what ive heard) doesnt change the sound very much..and they add a ton of power for a cat (ive heard they'll even add more power than a straight pipe..but that may just be a marketing ploy or environmentalists excuse to get one)

 

^ Magnaflow too

The ebay high-flow cats will increase sound (for better or worse, i couldnt tell ya), but i think they'll still pass emissions.

 

the ebay (no name) ones do the job, but they quickly deteriorate.