I took off the ducted carb heat system from my yellow plane. In doing so, I gained 200 static rpm from the loss of restrictions.

The anecdotal information that I have heard, and believe, is that the only planes which have ice issues are the ones with the ducted carb heat setup on them. This is due to the intake just behind the prop taking in the colder air. With the intakes by the firewall the air is preheated by the ambient temp inside the cowling lessening the likelihood of ice.

I have no scientific evidence to support this, but it does make logical sense.

The liquid heating type of carb ice prevention does seem to be interesting, though.