So I don't have much of a clue when it comes to identifying the EFI parts, although I do understand most of the terms.

Anyway, today I hear a backfire through the air intake when I started the car. I then noticed a roughness to the idle at the first stop light. Anything above idle and it feels better than ever as far as power goes and is running real smooth.

I get to work, and I notice the economy gauge is pegging halfway, even at idle, and in gear goes nearly to the red. When I get out in the underground at work I can smell the exhaust is running really rich.

So what am I looking at?

Vacuum leak (door and trunk locks ok, and no climate control)
Cold Start Valve
Stuck Injector
OPV (don't know if I have one)

Not that I'm going to touch it myself, I just like to have a little info before I take it to my Tech.

I have done a search, but I can't find much on the M110, or similar problems with the econo meter, rich running and rough idle.

Any help is appreciated