I just did my UP pipe install this past weekend. I bought a stock one and gutted it. (trying to stay stealth). I figured since i have everything else appart, I went ahead and ported out the ex. manifolds. I didn't port them as much as I wanted cause I had to have the car back together for work on Monday, but I made sure I worked on the short turn radiuses. I probably spent about 3-4 hrs porting just the drivers side ex.
I already had the Cobb stg 1 on the car, which made a significant difference. Not only does it increase the power, but it smooths out the entire RPM range. before, it was like the car had an on-off button on the boost, but the Cobb made it much better. The UP pipe did help the spool-up time and helped smooth out the acceleration even more. I can't tell if my car is any louder though. I guess I'm done modding my car for now. maybe once my warranty is up, I'll add a DP