One other thing you can do is drill into the minimum idle air rate screw cover on the throttle body and remove it. Behind the sealed cover is a Torx screw. You jumper the ALDL like you are reading codes and turn the key on but do not start. You will hear the IAC clicking. Wait about 30 seconds and unplug the IAC with the key on. I turn the key off, open the screw about 3 turns. Then start the truck. It will idle about 850 rpm. You can then bring the idle speed down to about 700 rpm. Shut off the engine and reconnect the IAC. The engine will now idle at no less than 700 rpm. Higher rpm = more vacuum and leaner mixture.