Idle control valve adjustment? TPS volts all over the place!!!

Q1 hey lads i have a 89 GQ SWB with a tb42 EFI with a ribbed auto, im sure this has been asked before probly a million times over and ive searched all over the net trying to find an answer but no luck, wondering if any body could instruct me step by step or post me a link on how to adjust the idle control vavle, ive been told it has to be done a certain way with unpluging the sensor then adjusting the idle screw, then reconnecting the plug to the sensor again, but been told different by others so im a bit stumped lol,

Q2 i had my auto serviced yesty cause ive had problems with it, changing gears at high revs, had a talk to the mechenic when i picked it up nd he said there is nothing wrong with the box its in perfect cond, although the tps voltage is all over the place when he tested it, so somewhere between the tps and the auto ecu the is an issue, has anyone had any anything happen to theres like this at all?
i know it sounds like a trip to the auto leackys but any info would be greatly appreciated
cheers
scott