If the MAF is out of the stream, then it will report LOW. Sooooo perhaps the gas rag worked because the reported MAF value was so low that the PCM did not add any fuel injector pulse. Then the motor started and ran just on the gas rag fumes.
Normally electrically disconnecting the MAF is a quick test to trouble shoot a possible bad MAF. The trick works because when the MAF is disconnected the PCM uses default values to replace the missing MAF values. If the motor still runs rich with the MAF electrically disconnected, this suggests:
- The PCM tune is NOT correct for the fuel injectors used.
- The fuel pressure is too high.
- The fuel pressure rail sensor is not sending correct valves.
- the fuel pressure sensor intake vacuum reference line is not connected or leaks.
Once stated, the motor may be able to run because the PCM will adjust the AF ratio using the O2 sensors in closed loop mode. This will show up a large negative LTFT values.
My 2003 GT did not have a built in test port on the fuel rails. It was necessary to install an in-line piece between the fuel line and the fuel rail.
Do you have an ODB2 scanner? It would really help to know what the PCM "thinks" the Fuel pressure and MAF flow is.
I don't see HOW a bad fuel pump could cause this. Bad fuel pump is normally associated with LOW fuel pressure. The stated symptom is pig rich.
Stop guessing and test the fuel pressure. Then you will know where to focus.
OBTW, one of the more common symptoms of a bad PCM is pig rich. However I recommend replacing a PCM only as a last resort. Replacing the PCM often causes as many problems as it solves.
I also remember helping someone with a high fuel pressure problem. The cause turned out to be a ground fault in the fuel pump negative return line. This caused the fuel pump to run at 100% all of the time.