2004 Pontiac Grand Prix Cold Start Problem-Must tap acceler

I have a well maintained car and I consider myself fairly mechanically proficient. But I have been totally stumped by this problem. I have scoured resources on the Net and can’t seem to figure this out.
Here is the Issue: Every time I go to start my Grand Prix, I have to tap the accelerator when starting the car. If I don’t tap the accelerator then the car won’t start. I checked my fuel pressure and I have a strong 56psi and the fuel pressure seems to hold after sitting for awhile. I have changed the fuel filter for good measure. I have scanned the engine and my scanner shows no error codes and shows that all systems checkout correctly. The car always runs well and gets decent mileage. I cleaned the pcv valve and map sensor seems to be good. Please help me out.