Quoting from the FSM "Introduction and Master Troubleshooting" section Page 9:

1. Before connecting or disconnecting the negative cable, be sure to turn off the ignition switch and the lighting switch. (If this is not done, there is the possibility of semiconductor parts being damaged.)
2. After completion of the work steps [when the battery's negative (-) terminal is connected], warm up the engine and allow it to idle for approximately five minutes under the conditions described below, in order to stabilize engine control conditions, and then check to be sure that the idling is satisfactory. For 3.0L engine models: If the engine rpm is high, switch OFF the ignition switch, and then, after switching it ON again let the engine idle for 2 or 3 minutes.
This will cause the engine rpm to decrease about 100 rpm, so repeat this procedure until the prescribed idling speed is reached.

Engine coolant temperature: 85 - 95 deg. C(185 - 203 deg F)
Lights, accessories: OFF
Transmission: neutral
Steering wheel: centered

There is also a section in the FSM MPI System starting on page 14-62 for setting the idle speed. Note that there are terminals to be grounded both in the engine bay and on the ECU test harness connector behind the glove box inside the truck.

Eric W.