That whole system was a true power killer. Even with it's four cat system, look at the bends and how many angles for flow direction before exiting. Just the 90 degree angles coming off the pre-cats after the exhaust has made it threw the first or two bricks in each line is a killer. No wonder the TQ levels raise dramatically once gutted or replaced. Are you putting that back on? Whats up with the rear glass tint? Do you have two Z's. Did you buy the gears already for the rebuild?