Pontiac Repair: 3800 series II misfire once engine warms up, mass air flow sensor, mass air flow

Question
I have a 2000 grand prix gt 3800 II k. The car runs good for about three minutes until the engine heats up. It still idles and runs good at low acceleration,but when you apply more pedal it misfires and fires into the exhaust. I have had the ignition control module checked,fuel pressure checked,new spark plugs, new plug wires, new fuel filter,and i also use lucas fuel injector cleaner. If i drive wide open throttle the check engin e soon light flashes about ten times but rarely stays on.Please help

Answer
Hi Mike:

2 thoughts. Unplug the Mass air flow sensor on the top of the throttle body and drive it. It will hesitate but see if it runs better once you get past the hesitation. If so the MAF sensor is bad. The second thought is the catalitic convery may be starting to plug up and causing too much back pressure in the exhaust. If I'm not mistaking ther is a special service policy for the converter for an extended warranty past the 8 year 80,000 mile base warranty.  You can can unbolt the front pipe at the rear exhaust manifold and drive it and see how it runs. if it runs better then that is the issue too much back pressure.
Good luck :)