Ok, I recently bought a 91 300zx twin turbo, and I decided I'd do a little research on the car and I've been trying to learn all about it and everything... but I'm really confused about "pre-cats" "cats" "down, mid, test & off-road pipes" and all that stuff... could anyone please explain all this to me?

Thanx

Dago

 

A "cat" is a catalytic converter which reburns exhaust fumes to further reduce your automobile's emissions, they also hurt hp due to their restrictive nature. The off-road pipes are merely a set up which allows you to divert exhaust gasses straight out with no catalytic converters or mufflers so it's VERY LOUD and basically no restriction whatsoever which can hurt hp in some applications.