Bad Fuel Pump or IAC?

ok im having a problem with my 2000 focus stalling out at idle, the car will go down the road fine when you are on the gas but when you sit at idle for a little while it will start studering and then finally stall out, it only does this once in awhile not always, im not sure if this is the fuel pump or the iac going out on it or not, i have been looking around the net and found that the fuel pump might be a possible recall on my year focus?? (not sure), also when the a/c or defrost is on the rpms are up and down, it will surge up and then it will studer down to almost stalling out, (not sure if that has anything to do with it or not, it might be the iac but im not sure), i have recently did a tune up (plugs, wires, air filter, fuel filter) so i know thats not the problem, all this has been going on for awhile and im been trying to figure it out but havent had any luck [dunno] , any help would be greatly appreciated, thanks