So I'm completely stumped with the wife's 2000 GTP. When I give it gas it takes off just fine until it hits about 20 mph and 2200 rpm's, then it falls flat on it's face. If I hold it to the floor, it will gain speed and a little more rpm till it hits 3000 rpm but so slow that I hardly notice it. I am however able to hold the throttle at a position around 2000 rpm and the car will gain speed at a normal rate too the speed I want but obviously at a rate that makes the drivers behind me not to happy. If I put it in neutral, the rpm's will go up to 4-5000 without a problem but nothing more. This did happen a few times this last summer and it seemed if I mashed the pedal to the floor for about 10 seconds it would fix/clear or whatever the problem, until now where I just can't get it to stop doing it. I have had it in the shop and they did a complete diagnostics check on the engine and found nothing wrong. Could this possibly be a torque converter issue? Plugged catalytic converter? I am open to any suggestions. Thanks in advanced guys.