Most of the time it's the fuel rail pressure sensor that goes bad. This is what I have seen. They run about $70.00 or so. You can check the voltage on it, if I'm not mistaken it should show about 4-6 volts..
Well Oreilly auto parts has them I looked it up, they have gone up in price. I would check Autozone local auto parts store. If you do not have a multi meter you won't be able to check voltage. Here's the link for the part, it's located on the left side fuel rail area. List: EFI Pressure Sensor - 2006 Ford Mustang | O'Reilly Auto Parts