Should I bring my 3.7" pulley to Carlisle, so you can try it out? I have it around here somewhere???
With a 3.0" exhaust, you will definitely lose a little of that low end torque, even with the supercharger on the K20a3. You'll scrape everywhere if you are only lowered 1.5"s. It will be LOUD with everything except the twin loop. Even the twin loop is slightly loud at times. I know this, because I've been running a few different 3.0" exhausts since 2006. But, you will LOVE the sound when you lay into the throttle!
If you insist on a 3.0" exhaust, just buy a cheapy no name brand. If it gets bent or damaged, you won't feel badly when it happens.
Cheap stainless 3.0" exhaust
*Maxbore will port your inlet housing and your thottlebody for about $200 if I remember what he quoted me. Just have him do it and it's all done and in one place.