Originally Posted by snrusnak
If sized appropriately, an x pipe, h pipe, and y pipe setup all are pretty close to equal in terms of hp/torque. Often times though people oversize y pipe systems and lose some low end power.
Don't listen to those who say you need back pressure for low end, or whatever else they come up with. That myth will never die. Regardless, it is false. Back pressure is ALWAYS bad for hp potential, you want free unrestricted flow. What most people don't realize is too big of a diameter exhaust pipe will slow down exhaust gas velocity, causing a loss in power.
I agree snrusnak, i have never seen a drag racing car (I am sure they are going for max hp and speed) with mufflers. All you see is fire coming out of straight pipes right off the engine.
I am thinking they know the scoop.