Free HP increase?

Stupid question, since I'm at work at 4am and bored out of my mind and thinking of ways to increase HP cheaply. I keep reading about people who are buying exaust systems that stop right before or right after the rear axle. If I was to cut my stock exaust near the rear axle will I increase or decrease my HP and torque?? I know Flowmaster has a set up where the exaust ends damn close to the axle and it has 3" tubing. I believe the stock tubing is about 2" and Flowmaster claims better performance etc. Wouldn't just cutting the stock tubing give it better performance with smaller tubing?? Just a thought that popped in my head. What do you guys think??