put it on a real scanner and ck it under "mode 6" all the sensors you are talking about wont make it do what your talking about. iac valve is a sore spot for ford, and it sounds like it is bad, and when they go bad they will not throw a code, and if it is not working right it can throw up lean codes, (p0171 and p0174), cause the iac is a controlled vacuum leak. p0171 and p0174 is in no way shape or form a code for a maf sensor and if the place that used the scanner told you that they are wrong. there is a different code for the maf sensor, also the old bosch iac valves could be tore down and cleaned, the newer ones cannot, they have a coating on them that can get messed up. also have someone get in the drs seat while you tap on the iac valve and have them put it in drive. most the time that will help it work, most of the time. also if you put it on a good scanner go under data and watch it when you put it in drive, or better yet, make a movie of it and watch it if it quits, that way you can see if it changes when you put it in drive. you can adjust the idle with a bolt on the side of the throttle body, it should be right where the cable hooks on there, another way of adjusting the idle is block the hole on the butterfly shaft, put a rivet in the hole to block it off.