I'd also check all your plug wires -- look for any of them that "at speed" might be being blown against a header and have burned enough to short. It doesn't take much!
You asked about under hood temps... and you should have an IAT - Intake Air Temp - sensor... which really isn't that important of a sensor - but would accommodate / allow for - intake air temps.
Also -- the MAP sensor is critical... the signal to this should come straight from a source with no "t's" etc....
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