First off, will a test pipe make a big difference instead of a cat? i have thermal 3" and a high flow cat. Also, would knocking all the **** out of a cat be the same as putting on a test pipe? thanks for any input.

 

the more HP you make, the larger the difference will be, but will still be a pretty small amount. (few HP)

 

for the little amount of gain you get from removing the cat, its not worth hurting the environment. Plus, withou the cat you car will smell like ****.