I got the rear cats removed Friday. The guys opened up the pipe to 2.5 inches as far up as they could to mate up with the catback and further increase flow. I know it's not my imagination, and it may be because I was specifically looking for it, but I can feel the small loss of torque down low and can also tell a decent difference in horsepower. Additionally, it sounds great. I know it's probably not loud enough for some of you, but it was exactly what I was hoping for. Most important, it didn't trip my check engine light. I know there was a question a while back from someone in NC about that. I'm actually registered in NC and during my last inspection the guys told me as long as the check engine isn't on I should be good to go. One of my buddies said it sounds like a totally different car, and a lady friend said for me to log on and tell you that it does increase hp. Granted that was just after going a fair amount sideways on a 1-2 shift