I can't comment on the engine running ragged issue but if it were mine, I would start by locating the modular plugs in the engine harness, unplugging, inspecting, cleaning & spraying each with a shot of electrical corrosion inhibitor and re-plugging them together. I've seen those plugs be an issue as many times as not. I would also check the switch/connections on the back of the engine instrument panel.
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-Shawn-
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