Engine runs very rough?

Truck will start but stall at first. Then if you keep rpm's up slightly for a few minutes she will run on her own. But pops or misses randomly. After driven a mile or so noises seem to clear and smooth idle. Replaced power steer pressure switch and brake booster and master cylinder, but brake pedal kind of mushy at startup then builds pressure after use light pumping. When driving. Engine idles up slightly when brake pedal first applied while parked. Also, truck has bad connection from exhaust pipe to front end of muffler. Does this affect engine idle? Cause missing and or popping/hiccups?

1987 F-150 4.9L EFI, Auto Trans. Problem: Engine missis when warm like is is just failing and will eventually die if left at idle. Runs OK till it starts to warm up, about 5 minutes. I have replaced the fuel in tank pump, high pressure fuel pump, fuel filter and have checked fuel pressure regulator for fuel leaks and holding 20psi vacuum. Will check actual fuel pressure and operation today. Replace EEC relay, plug wires, plugs, rotor, cap, coil and TPS(comfirmed at 1.0v). Could it be the MAP or Oxygen sensor and finally does this truck have an IRCM or CCRM?

Per your previous suggestion I have replaced the Oxygen Sensor. I also checked the fuel pressure and regulator response. It seems to work fine with pressure at 55psi engine OFF and low 40's engine ON. I removed the battery cable to zero out the EEC memory and started the truck. It ran better but still misses. It idled high at start and then brought itself down to a normal idle rpm. While driving there was an occasional miss during warm up and then the miss got pretty bad. It really didn't like acceleration when it was under a load. It died when I drove up and came to a stop. End of drive test. What do you suggest?

Duff

Could the miss fires be caused by the TFI Module of the Hall Effect Stater Assembly in the distributor? Duff

No Auto Zone parts house near me could perform the TFI module test. Purchased new TFI module and still no help. Found words on the internet to the effect that FORD had a recall for TFI and Distributor Stator assembles in the late 1980's. Seems heat from the engine was a problem so they moved the TFI to the fender to keep it cool. Put new TFI on rebuilt distributor and it runs better than before. Of course everything is new now.