Steve,

Have you checked your AFM pot? If it's showing infinity at idle or wild resistance variations at idle that could be the problem.

Also make sure you check the zero position of the AFM plate - key on. Exactly top of the tiny 2mm vertical cylinder in the AFM, position to check is furthermost from fuel distributor.

After that depress the plate to basic position (should be approx 0.1-2mm free travel - must have free travel) where you should feel the resistance increase as it contacts the control plunger. During this free travel you should see very little change in resistance at the AFM pot.

If the zero position is out it will affect mixture and the idle can do VERY weird things - trust me I know. To tune mine I set zero position, lean her out till basic is at the very bottom of the vertical cylinder (2mm), then richen her up (works out about .5mm on mine - or 1.5mm down the cyl) till she will start, then I being tuning her via Duty Cycle/EHA current.

As Duke mentioned check the throttle switch and the deccel microswitch for correct operation.

Cheers,
Neil