Wierd problem... please help

While accelerating or coasting .....sometimes both, my rpm's will drop to about 1500, and then when i push the gas...car will not accelerate.....i then have to take my foot off the gas then re apply it and then the rpm's shoot back up to normal....i just just changed the throttle position sensor and that did not help....any help???maybe the mass air flow sensor?????

What year and model Grand Prix to include engine size?

I have a 94 gtp that was doing the something except my rpms did jump and the car hesitated at first and then would go and all it was was the mass air flow sensor.