I partly agree with were to get the parts . I stopped buying anything from napa when in one day I got 3 bad alternators for one car and 2 bad startes for another , however , Parts Depot supplies the dealer. That same motorcraft part will cost about 30% more from ford. Parts Depot used to be Bumper to Bumper used to be Tropical. They supply ford and chevy dealers. You can walk in and buy what you want. Thats where I get all my parts. Most of the time a bad IAC valve will still do something if you tap on it. It might not work right but the RPM might change or shut off completely. When all else fails pull out the hammer