Lately I've been hearing a loud chuffing sound under heavy boost, which seems to coincide with the engine falling on it's face a little. Then the sound quiets, and the engine comes roaring back, followed by a repeat of the cycle - chuffing and falling on it's face. At first I thought this was a symptom of my exhaust leak getting worse (this post), but maybe I was just confusing two different problems. The exhaust leak problem has been around for a couple years, although I'm going to try to fix it now. The loud chuffing/roaring under heavy load is a newer problem that I at first chalked up to a worsening exhaust leak. But I don't think an exhaust leak would affect engine power when it is operating open-loop.
Has anybody experienced this problem before? The engine runs great, otherwise. It has a new MAF, supercharger isolator and oil, crank damper, crank trigger, water pump, thermostat and radiator, etc. It has been pretty well maintained. Could it be letting boost leak out under pressure through the lower intake manifold gaskets?
