Idle problems

I have a 1994 Toyota Land Cruiser issue that I'm hoping someone can help me with. When in park the idle is high one day and low another depending on the weather I think. Also when it is put in drive the idle drops 3grands but when it goes into reverse it drops about 5grands and causes the car to lug or jump. I replaced the idle control sensor ($280.00) and have the same problem. When driving down the road it runs fine until I need to stop. Can somebody please give me some suggestions