I am desperate right now. I bought a 1990 Volvo 740 GL a few months ago and have been chasing the same phantom problem ever since. Something is causing a low and rough idle, and harsh starting aswell as slow starts after stops. I have no idea what it is now. I have replaced up to but not only my MAT (mass air temp sensor as I’m running the Regina fuel system), o2 sensor, all four spark plugs and wires, the battery, the alternator twice, the starter (for the harsh start), and still cannot get rid of this problem. Someone. Anyone. EVERYONE please tell me something I haven’t checked yet or looked into.