I recently installed a 997 GT3 exhaust with valves on my car. It sounds much better and does not drone.
The issue I am having is I can't get the valves to fully close (I only get about 30% closed) as the engine (3.8 with ITBs/big Cam) does not produce much vacuum - about -4.5 at idle and -6 PSI when cruising at 3k RPM. Does anyone know a source for actuators that close with a lower vacuum? I put a vacuum pump on mine and it takes about -12 PSI to fully close -- if I could find one that closes at -5 or -6 PSI it would solve the issue. Picture attached of valves. I did wire them shut and went for a drive and the difference between fully closed and 30% closed is significant.
