my infiniti j30 has wierd idle issues need help?

[live life to the fullest]

i have a 1993 j30 with 110k and when i cold start the car it idles really high until it gets really warmed up then it goes back down? also the car idles very low whenever the engine is warm and i apply my brakes while im driving and goin for a full stop like as if its gonna just die out on me? also when its warmed up and its in park the idle sometimes goes up and then down on its own?