whats the differnce between a test pipe and a gutted cat. conv.

 

Acording to Sport Compact Car gutting a cat is not a good Idea since the sudden increase in pipe diameter will hurt your exhaust velocity and thus the scavenging effect. A test pipt,like the one I got for $50 in classifieds, is smooth and not restricting. run a high-flow cat for e-check and street