I got my RPI Full GT Exhaust installed last Saturday before the VRS meet.
Overall, I am very impressed with the exhaust's performance, the quality of the product, and RPI's customer service. I have no regrets.
I did a pre and post install dyno, and the results were very good. My base line was 327hp and the car was bone stock. My post install dyno was 351hp.
Performance wise, the car pulls harder thoughout the power band. I feel more torque, and the car doesn't have that "heavy" feeling that it once had. I don't know if anyone would believe me, but while driving to the VRS meet, I took the toll roads from Yorba Linda, the car felt more to the ground, the car felt more stable. I'm guessing it's the lighter weight, maybe it's my imagination. I'm sure all the socal peeps know that drive, it's pretty curvy with elevation changes, with open highway.
Sound wise, I like it. It is loud. To describe what it sounds like, I think it has 2 tones to it. It has that deep low tone at take off/low rpm, then a higher pitch a little bit raspy scream at WOT, and there is little drone. Personally, I think it sounds better in person. The week before the install, I had my buddies hear the exhaust from the Youtube clips, and one of them didn't like it. That changed when he heard it in person that day, and says the clips don't do justice.
I recommend this to anyone who's a performance enthusiast, an attention whore (you will get stares), and those who don't mind random competition from other drivers. It has made my driving more fun. Props to RPI.
Here is the dyno.