Are you
absolutely sure all the plug connectors are firmly pushed down on the plugs? The plugs are deep in the head, and it's easy to think the connector is in all the way. If you don't feel them snap right down, you can have a problem.
Also, the metal ferrule inside the Beru connector can be deformed, and is making poor contact.
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'81 SC Coupe (aka: "Blue Bomber")
Canada West Region PCA
The Blue Bomber's Website