8-11 is too high, 5-6 is the desired pressure. According to Roe and Fisher, in their "Rochester Carburetors" book, Quadrajets like 4-6 PSI at Idle, any more can cause problems. Checking the gauge accuracy is a good idea. What is the pressure when you hold the RPM at 12-1500 RPM, what pressure at 3500 RPM?
