Toyota Repair: High idle adjustment, toyota t100, toyota dealer

Question
I have just replaced the engine in a 1996 Toyota T100. It is a 3.4 engine. I replaced it with a 1997 4-Runner 3.4 engine.I kept the 96 plenum and put it on the 97 engine. with a few other pieces that were swapped. It starts and runs fine and even drives good. But it idles at about 1800 rpm. Also when I have it in park and press the gas pedal and slowly increase the rpm when it reaches 2500 and I hold it there it will run up to 3500 and then drop back to 2000 repeatedly. My repair Manuel say that the idle isn,t adjustable and that the ECM controls it. Is there maybe a sensor or something that I have missed in the change over or am I going to have to take it to a shop and get it checked on a computer to get it adjusted.

Answer
I don't think the computer part numbers are the same for the 4- Runner and the T-100 and that's where the problem may be, is there a way you can check the part numbers of the computers, if not contact the toyota dealer parts department and ask them for the computer part numbers for both of the vehicles if they are the same then there's no problem but if not I would suspect that this is where the problem lies.