Umm... in dyno tests, in NA setups, you'll see about 1 whp difference between test pipes and high-flow cats. You will also generally see a actual loss in torque if you gut your cat...

They (gutted cats and test pipes) sound like ass, and I can tell from 100 feet behind a ricer (on the freeway) if he's gutted his cat... it smells so bad...

Spend the money and get a cat... it's better for the environment, and your car will gain power while not smelling like ass or sound like shit.