1994 GMC Truck

Engine Performance problem
1994 GMC Truck 6 cyl Two Wheel Drive Manual 320, 00 miles

I also have a PU that had the same problems as the Sable. It all started with bad gas. Anyway, I also changed the plugs in my truck, today, because it was coughing and backfiring, and now, I can't get up any speed. It sounds like a machine gun and won't get over 40 mph. It's a 5 speed and I didn't have THIS problem before changing the plugs. Did I do something wrong?

July 9, 2010.

Possibilities: Inspect and test all the following listed below: Oxygen sensor.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Crankshaft position sensor
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
False air leakage.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note: If it doesn't apply disregard

Jul 9, 2010.
Inspect and test the throttle position sensor

Jul 9, 2010.