Be sure the plugs are clean. You want idle vacuum as high as possible and steady. Then slowly adjust the idle AF upward a tenth at a time to help the vacuum - giving the adaptive learning time to adjust maps. Re-adjust timing to get more vacuum. The vacuum needle will become erratic if the timing is too high. You may be able to take the initial timing to 20 or more initial degrees. Just don't try to rev the engine - higher RPMs could cause pre-ignition and detonation until the slope and distributor total advance is reset.