Ford Repair: 91 F-150 engine misfire & back fire, throttle position sensor, air control valve

Question
Just bought a '91 F-150 with a misfire. I replaced the spark plugs, wires, cap, and rotor. I checked the timing and the firing order and everything is the way it should be. The truck has a miss through out all acceleration and it backfires when you accelerate it wide open throttle and release. Put the car in the scanner and the scanner gave me codes: 22, 33, 44, 13 & 12. So I replaced the MAP sensor and I bypassed the EGR valve but it didn't fix the problem. Extremely frustrated about to push it into a canal PLEASE HELP!!!

Answer
You're problem appears to be in the throttle bosy. Neither you're idle air control valve or throttle position sensor are in range. Excessive carbon buildup happens around the flap inside the throttle body. Set the EGR back the way it was. Clean it out with cleaner, and let me know how that goes. On another note, the backfiring is troubling. Are you sure it is backfiring or is it popping and "bucking"? Backfiring can come from a three things. A defective intake gasket, incorrect ignition timing(timing chain related), or a worn cam.