I have a pace setter H pipe for my 1990 stang. Here in california they are really hard about passing smog, and I was wondering what kind of UPGRADE (if i can make any) could I make that would make my car street legal. I know I need catylitic converters, so i was thinking about going BBK Catted X pipe so that I can still savoir some performance. But will having the high flow cats slow my car down from having no cats at all and straight tubing? does anyone who had different types of exhaust and dyno numbers know the difference? No one seems to talk about it. I know I gained a substantial amount of hp with the straight pipes, but I need something more practical in a state where if I get pulled over I am kinda screwed. BTW. another quick question, what size headers should I upgrade to for mild performance? 1 5/8 or 1 3/4. I am only looking to maybe press the 300 hp marker at most. Maybe 350 down the line, but nothing too radical because this is my everyday driver... until I find something else. OK thanks