4) Carb Heat:
At the end of doing all the good things that BPF suggests a check should be made to confirm that the RPM has returned to exactly what
it was before Carb Heat was first applied. If RPM higher then it suggests
some ice was present and has now melted. However it is impossible to know
if ALL the ice has melted - so reset RPM to POH suggested figure and repeat
the Carb Heat check. Not sure what it means if RPM is lower after Carb Heat
check - possibly Throttle Friction too loose?
If engine runs rough when Carb Heat is applied this could be due to ice melting and water running through engine or it could (in those aircraft where the exhaust provides the heat) be due to defects in the exhaust system allowing "pre-burned" (less O2) air & combustion products in to the induction system.
5) Mixture:
Sounds like a good system check but I am unaware of it being required
in any POH - or of it being performed in practise?