Hook up a fuel pressure gauge to the schrader valve on the pass side fuel rail. Watch pressure while its idleing or while someone throttles it.

 

I took out the IAC (bottom screw is kind of a PAIN) and it looked like it had carbon build up on it. I am going to mst likely replace it.

One more thing. I remember last night that when I would rev the truck up, the idle would come down real slow. I re-installed the old IAC and it did that once, but now it acts a little more normal. I read my manual about IAC's and that sounds a lot like the trouble I am having. It was only giving me trouble when I was stopped.