I wonder if the higher CHTs have anything to do at all with the alternate induction air system.  Seems to me that if you are taking on significant ice you have two factors that will drive up CHTs:

1. Ice on the engine cooling inlets on the cowl disrupting the flow.
2. Significant reduction in indicated airspeed that reduces the cooling air flowing into the cowl.

I think #2 is probably the biggest deal.  Larry mentioned that his airspeed can go down as low as 120KIAS.  If full cruise power is maintained at this airspeed I bet your engine will overheat no matter what the mixture or induction air is doing.

George's suggestion of a test of the alternate induction system in non-icing conditions is a good one -- rule it in or out as a culprit.

Just some musings from a lowly 320 driver...

Dan Olsen