Does anybody know where I can find independent information/testing on the major exhaust manufacturers. I'm curious as to wether or not there has been any testing or side by side comparison done, something similar to what SCC has done for the Celica and WRX(i think those are the cars).

I'd like to make a decision based on actual hp and torque gain(and where in the rmp range), weight, pipe diameter. you get the point.