FFF
There is a small venturi by the throttle butterfly which adjusts fuel flow automatically. This could theoretically get blocked if there is ice around the butterfly valve. I have never heard of this being a problem in practice though. Appropriate use of Alternate Air will make sure it is not a problem.
It is difficult to explain the fuel metering system in this forum, I cant really explain anything to do with flying without a white board and 4 colour pens! The best way is to make your friendly QFI a coffee and get him to explain it.
MM