I am installing DC 4-1 header, and an Apex N1 cat back 2.5" exhaust on monday. If i dont install a high flow cat at the same time would i not see gains?? or would i with out a high flow car?? TIA....

 

unless you have some major mods or a turbo .... a high flow cat wouldnt help you much. You'd be better off sticking with your stock cat.

 

You'll for sure notice a power gain with using the stock cat. Since your using a 4-1 header and n1 exhaust (both meant for top end power gains), it will be mostly gains in the top end at high revs. Using a high flow cat will have a little effect on the power, i pretty just noticed quicker revs and the exhaust was louder.