Absolutely on the power increase. I did a pulley first and believed I could feel that. The gain from the exhaust was more dramatic. I did not think it lost anything on the bottom end. I totally believe the +20 to +25 rwhp results most people get from a catless x-pipe. My rear exhaust is stock. I have yet to see any dynos of gains from rear exhaust changes, though people seem to like the sound changes. Even BMW makes no power gain for its $4000 rear exhaust, and claims only a more powerful sound. I daily drive the car so I want a civilized sound.
I have not been on the dyno to verify, but I will say that I thought the car was a bit slow before and now I think it is OK for a driver. It goes pretty good.