Check the throttle linkage to determine that it permits everything to return to full idle (all stops are contacted). Frequently, the linkages are bent/misaligned such that the idle stop is not contacted. I would remove all of the throttle linkage balls from their sockets to determine if the engine idles at the proper speed. If it does, then one or more of the throttle linkages are bent/misaligned. Don't condemn the idle computer/idle vale until you have performed and passed this test. Mark