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Not exactly sure which distributer or ecu , but it is MEFI 3.maybe....any idea which distributor is used? which ECU (MEFI-x)?
jumpering A & B gets you into service mode, whichs locks the timing and, depending upon the program flashed in, may raise the idle speed.
when you exit service mode, the ECU resumes dynamic adjustments of the timing and all the other adjustments. you can find the Delphi MEFI-3 manual on the www with a bit of searching....it provides more detail than most people want.
As far as "other issues", you can "read the codes" from the ECU while in service mode...if there are no codes saved, then the computer doesn't see any problems. the bad news is not everything needed is connected to the computer.