I'll have to go back and look how I done it, but I rerouted the vacuum control lines to make the pump exhaust through the by pass muffler after I kicked the cats out the air that was going into my heads made for a lot of popping in the exhaust when it was routed to the heads and made a whooshing noise when it was routed to the pipe that had been hooked to the cats. so I sit down with the shop manual and figured out how all that worked and made it exhaust all the time and plugged off the other vacuum lines. I plan to get a pump delete pulley kit but Just haven't done it yet.