Help! 7 Days $700 and Still No Clue

[JumpedInTheDeepEnd]

Hi there. As my name would suggest I really did jump in the deep end on this one. I recently bought a 1988 F150 4.9 I6 Manual from an individual owner. It has about 160k miles in it. The truck ran fine when we picked it up. All symptoms developed over a period of 2 or 3 days and have gotten progressively worse, before being parked.

Symptoms
Lopes and tries to stall but smoothes at higher rpm.
Seems to miss on one cylinder.
Heavy Black carbon deposits on all plugs.
IAC and O2 sensors helped cut back on the black smoke, but did not solve the problem.

Vacuum
-Replaced all vacuum hoses
-Checked for leaks at or around the throttle body
-Is pulling 29-30 in Hg. at manifold vacuum tree and similar throughout

Ignition
-Replaced distributor cap rotor
-Replaced wires and spark plugs
-Good spark off ignition coil
-Checked timing
-Checked compression 150-155 psi. on all 6 and holds

Fuel
-Checked fuel supply pressure 48 psi.
-Fresh fuel

Valves and Sensors
-PCV valve and filter replaced (breather valve on my model)
-Idle Air Control replaced (IAC)
-O2 sensor replaced (as far as I know my model only has one)
-Throttle Position Sensor replaced
-EGR appears to be good
-Took battery cables off for mater reset

General Maintenance
-Serpentine belt
-Radiator, thermostat, upper and lower hoses
-Upper and lower heater hoses

I would greatly appreciate any input or ideas. Cause I am all out.

 

[blacksnapon]

First thing I would look at is a coolant temp sensor/sender. If the module thinks the engine is cold, it richens the fuel in an attempt to warm it up faster. Correct thermostat is a must. 190/2 degree is a must.