2004 Ford Mustang skips

OK I first need to know what other mods have been done. I also would like you to clean the mass air flow sensor (only use mass air flow cleaner). Get back to me with how the cleaner goes and the other mods that have been done so I can better help. I also need to know what type of charger is it like a procharger or ? and how much boost?

It's a 2004 Ford Mustang Mach 1 with procharger p1sc. We currently have it at a repair shop, but aren't feeling confident they are able to really assess the problem. They replaced the IAC motor last week, said it is a common problem with Fords, because the car was not starting every time. We are not sure of the boost, think it is 10lbs. Just bought this car a couple of weeks ago in another state!:( My husband has been looking for years, and we finally had the finances, hope we haven't made a huge mistake. It is a beautiful car! But not much good if it doesn't perform! Will follow up when we get back, and ask them about cleaning the mass air flow sensor. Thanks

Ok on the iac motor it is not so common in the newer vintages. I have never had a problem with mine and it is a 98 with about 160 thousand on it and love driving it. You said it don't start everytime? What do you mean does it crank over and just not start or does it do not do anything at all?

We picked up the car today. The repairman said "found lean condition when cold on hard acceleration, most likely calibration problem with supercharger" He suggested we take it to Charlie Potter Racing and have the ECU programming recalibrated, that guy referred us to The Muffler Shop for this. What do you think? Are we in the right ballpark? Thanks.

No I don't think that will work they don't know how to deal with an aftermarket super charger so they are passing you around. With a mass air flow unit and keeping it below 11 psi boost the mass air flow will pick up the incoming air and read it and compensate for it. If you would do a few things for me we can figure this out. First unplug the coolant temp sensor and ohm it. Get back to me with the ohms and the engine temp at time you checked it (if the engine is cold then air temp will do). Did you clean the mass air flow unit yet? Has any of the rear O2's been checked or replaced? You may end up having to buy an aftermarket mass air flow unit that is bigger but lets get some info from the car first. One more question has the check engine light come on?