IO540,
There's another thread about carb heat, in which I explain that the fuel flow does not decrease when you apply carb heat (or at least, not appreciably). However, I think that when Chuck says: "Normally you get a drop in power with carb heat due to the hot air enrichening the mixture" he is over-simplifying things slightly.
The application of carb heat reduces the amount of air going into the engine, which (ordinarilly) reduces the power output.
Because the fuel flow doesn't change, you also get a richer mixture. Now, if the mixture was too lean to begin with then the lean mixture would cause a lack of power (as well as engine damage). In this case, when you apply carb heat, not only will you get a reduction in power because of the lower air flow, you will also get an increase in power because of the more efficient fuel burn due to the more appropriate mixture - and the increase in power may well be more than the decrease in power, resulting in a net increase.
At least, I think that's what Chuck is getting at.
FFF
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(PS - Chuck, hope you don't mind me jumping in. Explaining it myself usually helps me get it clear in my own head, though.)