it helps balance out the exhaust pulses for smoother flow (smooth flow = more horsepower) and helps reduce resonance. The closer you can get the crossover to the engine the more effective it is, but most pipe shops put it behind the trans so you dont have to drop the exhaust to work on it.

 

i went with a DR.gas x-pipe with spin tech mufflers.... my auto teacher used that on his fox body race car and he told me that it create tons of toque and H and the same time i can t wait to get it on my car