I recently had the error code p0033 on my '07 Grand Prix GT. The fix was to replace the solenoid on the supercharger. I purchased the part from a local GM dealer for $43.75, as it was difficult to find from the big name part stores. Part number 1997244, description "Valve, Supercharger Bypass." I attempted to order it online from Napa and after a week and a half they told me the part is being discontinued.
You pretty much have to destroy the vacuum hose that connects the solenoid to the actuator, so you might as well pick up new hose in advance.
Thanks to all who have posted on here. I'm not the type who works on cars much and it feels good to get out of this relatively cheaply.