GM-GMC: 90 G30 cargo van, vacuum leak, plug cable

Question
My problem started when my van won't shift to reverse until the engine warm up, until it won't shift to 3rd gear while on drive. I had the transmission overhauled, changed the spark plug, rotor, dist. cap,and plug cable. After all that work, that day I drove the van home, I noticed that  the idle is too high. I checked vacuum leak, and it's all ok, I don't know what else to check. I'm thinking of something wrong with the new overhauled trans. or maybe the computer? Please advise.

Answer
There is a idle sensor . These go bad and the idle just races at times .. Try to look at this . I would bring it back and inform them that the engine was not racing at idle prior to the repair work being performed on the transmission and additional engine tune-up work ... They should fix the idle problem ?NO CHARGE