I have found that setting the sensor to a specific voltage doesn't work too well. The way that I have always set the TPS baseline is this. Run the truck up to operating temp, shut it down. Unplug the connector at the idle air control. Restart the truck and run it at 2500 RPM for 30 seconds, let off and observe the idle speed, it should be around 750 RPM. Adjust the screw until you achieve this, give the throttle a quick snap after adjustment to seat the throttle arm against the screw properly. Once you have set the throttle to 750 rpm, shut the engine off. Restart the engine and run it at 2500 RPM for 30 seconds again, Verify that the idle is still at 750RPM. Shut the truck down again and reconnect the IAC, disconnect the battery for at least 5 minutes, reconnect the battery and you should be set.