there are no #s....would be a pain in da ass to swap back and forth. It doesn't take a genius to look at the huge difference and the gains by looking at them. You can even see that the pre cat blocks off part of the turbo housing. With the pre-cats the exhaust hits brick walls. They create alot of turbulence with the 4" hole of the pre cat making the exhaust harder to flow through. If you want more details talk to Greg. It's incredible when you hold them both in your hands. Talk to guys who have gone from gutted pre cats to G.D. DPs...they r on here.
