1999 Intrepid stalling-This is stumping the dealer

I have a 1999 Intrepid 2.7 liter 6 cyl with 139,000 miles.
The car will sputter as I'm driving and stall. I try to restart it and when it does, it runs real ruff(rpm's at 500) and when I mash the gas it stalls. After about 30-60 minutes I try to restart it and it runs fine for a few days and we start the process all over. First time at the dealers, they chaged the plugs and MAP sensor. Second time at dealer they unpluged the AC Pressure Transducer-next day same thing. It is again at the dealers and the scanner states- MAP Voltage High(P0113), Intake air Temp sensor volts High(P0300), Multiple Cylinder misfires. They say that all these senor code share the same ground on the computer. The mechanic today(5/30) drove it for 60 miles and could not reproduce the problem. They said they were going to test the pressure of the fuel pump. I don't know the outcome of the pressure test for the fuel pump. The check engine light does blink then stays steady. Sometimes when I sucessfully restart it the check engin light is off. HELP!