bad idle issues ka24e

[DvlDuk]

model: 89 240sx engine: ka24e

problem: what is going on is when i start the car it will idle up to about 2000-2500 and then it will idle down to where it dies. if i keep my foot on the gas it will stay running until i let off. also if i run it for about a mile it will stay running at an idle but it coughs really bad and tries to die but wont. i have run fuel pressure and compression tests and they all pass. about 3 months ago i tore the engine apart and replaced all the gaskets and it ran for about 2 months just fine and then one morning this started. any suggestions? thanks

[MaximA32]

Check the throttle position sensor and the MAF.