I don't think your car has a MAP sensor. There are two ways to measure air into the engine. One is done with mass air meter (maf) and the other with a manifold absolute pressure sensor (map). Fords use a MAF..
There is a fuel rail pressure sensor on your fuel rail perhaps that is what you think is the map. This sensor keeps the rail pressure at 45 psi above the manifold pressure. So you see a vacuum line on this sensor, but it is measuring fuel pressure relative to manifold pressure.
Can you check the fuel pressure? There should be a fitting on the rail that looks like a tire valve. connect a press sure gage to it (some autoparts stores will loan them) and make sure it stays above 45 psi all the time.
Your fuel pump might be getting weak. I had a Ford Windstar did the same thing and had to put a fuel pump in it.How do you know if your map sensor is bad?
You can generally tell when your O2 sensor is bad with a diagnostic scan. Your problem however seems to be with either fuel delivery, ignition, or air intake. Unless you just don't know what a slipping transmission feels like. Do a fuel system pressure test to make sure its within specs. Im not familiar with the V6 mustang, Im going to assume it has a coil pack ignition. Check it or check them all(whichever you have). Make sure your air filter isn't clogged up.
