If it seems to be pig rich, check the collection of solenoid valves behind the battery. One of the items in there is the MAP (Manifold Absolute Pressure) sensor. It needs to have a good vacuum signal from the intake, any cracks or leaks in the line from the fitting on the upper plenum to that will make the system think you are at wide open throttle and go full rich.
The other item is grounds, on the 1985-86 5.0L EFI the entire system grounds to the battery negative post. Wiring on these is also a problem, I have seen a number of these where the insulation has crumbled. The injectors are set up as two groups of four, four end (1458) and four center (2367), if only four of the plugs (one of the two groups) are badly fouled, one of two things, a grounded control circuit for the injectors or a bad computer.
Bill AKA "LOBO"
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"Getting old is inevitable, growing up is optional"
Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator
Wife's 2011 Flex Limited
Daily Driver 2009 Flex Limited with factory tow package
Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413