Good Chance this is caused by a faulty O2 Sensor. I had the engine light stuck on in my 2002 Montana and replaced rear O2 sensor and it turned it off.
"http://wiki.answers.com/Q/What_causes_your_2006_pontiac_grand_prix_driver_info_center_to_display_reduced_engine_power"
It needs to be Re-Set.. Most places can do it for no cost. takes less than 10 seconds.
What causes a 1998 Pontiac transport to run hot and engine shuts off
The most likely problem is a Head Gasket. Sorry Man.
put on a new PCV valve.
What causes a 1997 Pontiac sunfire gt with a 2.4 liter engine to stall when stopped at a light
Low Coolant. Poor coolant circulation. Intake gasket. Head gasket.
You are OVERHEATING. You most likely have an intake or Head gasket problem.
One of the possible causes of a Pontiac Bonneville to jerk during acceleration is that the car needs a tune up. The engine misfiring can lead it to jerk as you accelerate.
Could be low coolant, stuck thermostat, bad heater control head (if climate control)
probably a bad camshaft sensor.