Ford Repair: 1984 MUSTANG GT, anniversary model, fuel pumps

Question
I HAVE 5.0 SINGLE EXHAUST,FUEL INJECTION IN THE CARB.WHEN DRIVING AT A STEADY SPEED, THE SEEMS TO PULSATE,SOMETIMES AT IDLE THE RPM WILL RAISE AND LOWER WITHIN 200/300 RPM.I HAD THE FUEL SYSTEM CHECKED AND BOTH FUEL PUMPS WERE REPLACED.NO LUCK! I HAVE HAD THE CHECKED FOR AN ELECTRICAL PROBLEM BUT EVERY SINGLE TIME I HAD THE APPOINTMENT, THE CAR RAN FINE.I PUT UP WITH THE WAY THE CAR RUNS UNTIL I GET AGRIVATED AGAIN.PLEASE HELP WITH SOME SUGGESTIONS.THANK YOU IN ADVANCE FOR YOUR COOPERATION IN THIS MATTER. PS: ALSO REPLACED EGR VALVE,O2 SENSORS,WIRES,PLUGS,FILTERS AND ELECTRONIC MODULE ON THE DISTRBUTOR  

Answer
Bob-

  The most common cause of problems like this on Central Fuel Injection (CFI) cars like your is the MAP sensor or Manifold absolute Pressure sensor.  Your car actually doesn't have a carb.  It has a throttle body with 2 injectors feeding the manifold.  The MAP sensor's job is to measure the barometric pressure at the manifold and compare it to atmospheric pressure and use that measurement to adjust fuel and timing.  I personally own an '84 GT350 (the 20th anniversary model) and before switching to EFI I probably replaced the MAP sensor at least twice.  Hope this helps.

Steve