Originally Posted by Phimosis

Don't need a CARB expemtion order for cat-back-exhaust. You do need them for hi flow cats and headers though.

Another side note: CBE exhaust are only good for about 5hp based on dozens of before and after dyno results. An yeah, I get that a SC engine will flow more exhaust and be more restrictive, but it's going to be how much, 7hp difference?

Another side note: There's no way to know which kit is making more power without running them back to back on the same dyno. I have seen as much as 40hp difference in readings on my own car based on temp, alt and dyno manufacturer differences. One of my dyno guys says you can tinker with the settings to get the dyno to read higher or lower as well.