4.0 idling problem

[Brian25]

have a 94 ranger with a 4.0. one day my truck started idling funny when i was driving if i came up to a stop the RPMs would stay about 2000 rpm then drop a few secconds later and stay where they were suppost to. i have replaced the IACV the TPS cleaned the MAF took the upper intake manifold apart and cleaned it replaced the EGR valve. i have checked the whole truck for vaccum leaks and i still cant figure it out. now if i disconect the IACV and drive like that the truck acts like its suppost to could my computer be bad??