i had an 84 vette i ran with cats, and then straight pipes. i loved that thing. it was setup that way when i got it, so i can't compare power before and after, but it was definitely fun. i want to get my gto to sound similar one day...only legal.
I have a x pipe back to 2 1/2 straight pips.. sounds good under load, but i HATE the poping and gargal i get off deceleration*. I am going to try to look for some magna flow's. i didnt notice a gain or loss with the change from stock.. guess i will need headers and delete cats for that.. good luck!