Strange.
I've had this prob on both my sc and my old xr7. On the SC, the hose clamp that connects to the bypass valve mysteriously came outward, thus, causing the valve to get stuck and making the car run n/a. At first, I figured my blower had seized. Took me about a day of looking to notice it. On my old xr7, I had defective plug wires which caused a bucking condition under boost conditions. Also, on the SC, I used some Bosch plugs and experienced the same thing, bucking under boost.