It seems you have honed right in on the problem. When I got the car I noticed the clip holding the idle control unit was in place but the nut was missing(it appears there was one nut on the drivers side and a clip on passenger).Which leads me to think it was fooled with. I did mention this to the mechanic but he seemed to think since the surging and associated bucking happened at all ranges of acceleration that it was not the problem. However, I will check the harness and if i can open the thing up & check the board as well. Thanks