mickmate You can save yourself alot of time and money by doing a backpressure test on each exhaust system if you are looking for just power. They have a gauge with an O2 sensor end on it. Drill tap and weld a bung to the pipe between the collector and the muffler. Go out for a test and look at the pressure reading at WOT If the is no pressure you are hurting the motor and lossing power, you are looking for 1-2.5 psi of pos+. This is where the most power will come from the motor. There are some varibles on this. Size of motor and any power adders. Anything over the 3.0 is lossing power from the exhaust system. This way is a quicker and faster way to test exhaust systems. Most exhaust systems ( sidepipes ) are toned down because of noise. Some cars need an ear plug in the L/S ear unless you like the ringing after you have been out of the car for an hour. Will someone answer the phone!!
Side pipes can cost anywhere from 10-40 HP at the high rpm band. Under normal driving and up to about 4,000 rpm with a 427 cube motor stock you only loose a 10 HP. The less the back pressure the loader the pipes. Rick L.