Did this problem begin shortly after making any changes to the car?
Just guessing at some things to look for:-
Do any of the wires for your AFC run close to the shifter or shifter cable? If so, there could be a short there.
Check out your MAF wiring/harnesses for anything untoward.
With the car idling in Park, grab the MAF/AFC harnesses/wiring at various points and move it around some to see if the engine will stall. If it does then it could help you track down a wiring fault.
Was ALL your AFC wiring removed when you tried that? or just some of it.
I'm thinking you have an electrical fault that occurs in foward gears because of either the shifter cable moving (and in turn moving the wires) or because of the engine torqueing over backwards slightly and moving the wires.
Check fuses, especially the one for the auto computer if there is one.
While you have your multimeter out, check the MAF ground resistance.
Unlikely but just have a look inside the sensor hole in the MAF and see if there is any dirt or whatever in there.
Don't forget to watch the WRC on channel 3 tonite!!
