Been very close to your situation and not too long ago.

I live in Minnesota, and the last few things that went haywire were the following:

Fuel Pressure Regulator - was 3 time higher than what it should have been
Wouldn't start under 0 degrees F.
Distributor Cap - just crap
Rotor - crap again
Injector relay - ??
The last three manifested itself when I could push start the car
but couldn't start it with the starter. -talk about wierd?!-

Don't forget to check all of the plumbing between the AMM and the actual intake. If there is an appreciable hole (shouldn't be any!) then the AMM can be good, but not in the system so to speak. i.e. effectively bypassed.

If you want to know how about your rich/lean AF mixture scene - check your plugs. Heck it may be time to replace them anyway - that is if your 'major tune-up' didn't include them.


Good luck -
Make sure to get the Haynes manual - they are better.
Checking the AMM is pretty easy - the ECU is located on the wall of the right foot of the front passenger.

Pete