I've personally never encountered a vacuum leak that set a code for a MAF, but I'm not sure it couldn't happen either.
A vacuum leak lets in air that the computer can't account for (MAF is how the computer calculates airflow into the engine)
Also, are you getting the misfire from the tail pipe or the intake manifold? Did you check your ignition system? (Including timing) I'd go ahead and do this first, just to eliminate it as a possible source of trouble.
Next do another pressure test. This time with the Key on/Engine off. Make sure the pressure holds steady for at least fifteen minutes.
This is to check for a leaking fuel pressure regulator and leaking injectors. If the pressure holds steady, then do a balance/drop test on the injectors one at a time. If these check out, then start looking at the other sensors of your engine, (crank/cam, coolant, MAP, TPS, etc.)
Sunday, March 7th, 2010 AT 7:48 PM