My 740 non-turbo has Regina fuel system. No driveability/performance problems. Checking diagnosis codes (just a routine look-see), it gives the control unit fault code. Tried clearing it through the code flasher unit, and by pulling the negative battery cable, but it keeps coming up. No "check engine" light. I have cleaned and re-made all engine and control unit grounds. I'm in the "if its not broke don't fix it" mode, but I would appreciate any feedback.