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On your 1986 F-150 5.0L EFI, the SPOUT connector (Spark Output) is a small, usually gray, jumper plug found near the distributor, often within 6 inches, connected to the TFI module on the distributor itself; disconnecting it lets you set base timing by turning off computer control, usually to about 10 degrees BTDC.
See if disconnecting the spout connector makes any difference.
Jim
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