[Sharkstooth]

You said you fixed the overheating problem by replacing the fan,but did you replace the head gasket.It is possible that you have a leaky head gasket causing the idle miss and if you think about it when it warms up the aluminum expands and the leak becomes worse causing it to run worse.The reason why i say this is because i had a car that did this and did not show signs of it like smoking or smelling like antifreeze,than all of a sudden it got worse and would go through a gallon of water a day and still would not smoke and had no water in the oil and the car still had great power.When i took my camaro apart,it was leaking out of a little water jacket hole in the head gasket.I put back together and the Idle problem and losing water where fixed.I know these are two different cars but the same concept,good luck.