Q: Truck wants to turn off when first stepping on gas.

Your idle RPM is out of range high. The RPM fluctuation could be due to a vacuum leak or a sticky throttle plate or a malfunctioning idle air control valve. Indeed, faults in those components could cause the lag on acceleration and the stalling. Another possibility is that there is still a fault in the manifold absolute pressure (MAP) sensor circuit. The MAP sensor detects engine load and generates a signal that is proportional to the amount of vacuum in the intake manifold. The ECU uses this information to adjust ignition timing and fuel enrichment relative to the amount of power needed. When the engine is working hard, intake vacuum drops as the throttle opens wide and the engine takes in more air, which requires more fuel to keep the air/fuel ratio in balance. When the computer reads a heavy load signal from the MAP sensor, it adjusts the fuel mixture to slightly more rich than normal so the engine can produce more power. The computer will then retard (back off) ignition timing slightly to prevent detonation (spark knock) that can damage the engine and decrease performance. If the MAP sensor circuit is faulty, this foregoing sequence may explain why the engine stumbles or dies as you put a load on the motor. YourMechanic offers a stalling diagnostic which covers all the potential causes of engine stalling and hesitation that your car is experiencing. If you request that service a certified Mechanic, dispatched by YourMechanic right to your location, will get this problem resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.