The Fuel Pressure Regulator(FPR) on the fuel rail has a vacuum line, remove this line and check if for gas or gas smell.
FPR diaphragm can leak and raw fuel will be sucked into intake via that vacuum line.
You may have a fuel injector sticking open.
Hard to pinpoint that issue.
OHM test on injectors should show between 11-16ohm, but that test is for a dead injector.
Sticking injector could be a broken spring, no test for that.
Also the fuel injectors get 12volts when key is on, the computer opens them by Grounding them
You should have Batch Fire injection, than means the computer only has 2 Ground wires for 6 injectors, so computer opens 3 injectors at the same time.
My wiring diagram shows a Light Green/White stripe wire as one Ground(injectors 1, 2, 4) and a Tan/Red stripe wire as the other Ground(3, 5, 6).
IF....Big IF, one of those wires was chaffed and was intermittently Grounding to engine, firewall, body, etc.........then 3 injectors would open at that time, flooding engine.
You can pull off an injector plug and test for a ground while moving wires around.
Next is the computer, pop the top and have a look inside.
Good info here on pins and circuit board:
http://www.auto-diagnostics.info/ford_eec_iv
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