88 XJ 4.0. new tps. new cts. new iac. still idles at 1000rpm in gear. seems pretty smooth now though but all my friends jeeps idle at like 500 or 450 in gear. what the heck is wrong with mine. new wires, plugs, cap/rotor. once when i tried the iac i pulled it, cleaned it and put it back in and it idled perfect. next day it was right back to normal. tried oiling it the other day with no change. then switched with my friends jeep that runs fine and still didnt fix it. could it be vacuum? what do i search for? help!!!