rpms do not drop between shifts?

2001 p.p plenum and throttle body. ok i noticed when im going in between shifts the car does not drop in r.p.m like it should. when you come to a stop it will idle around 1 1/2 then it will decend to 1/2 where it should be. its really a pain when i need to stop in a hurry feels like the car is getting pushed until the rpms drop. now i did not touch anything on plenum or throttle because when i first installled everything it was mint. but thats when it was much cooler outside now the weather is getting warmer could that have anything to do with it?

i seen a reply on here that a guy tried. ok pull off negative battery terminal,hold brake pedal for ten seconds re-connect terminal,let ac run for 5 mins and then the heat for 5 mins and reset clock,but my clock was not effected. now the car seems alot better, but i still get a little hang up but the difference is alot better. i also seen a threat on here about making your own iac plate, but im gonna wait a little bit just to see what happens.