Idle air motor will problems not make your car run rough. It only affects the idle speed. (too low or too high). Could be your butterfly valve. I believe it is in on position and then flips to the other position above a certain rpm.

I am betting on electrical. Your cheap plugs may be the problem. You really should have double platinum plugs in there. How many miles on your truck? How old are your wires?

'90 Montero XLS (Sold, sadly)
'95 Montero LS 160k
'03 Montero Limited 30k