2002 Ford Escape - MAF

I have a 2002 Ford Escape with only 40,000 miles. I treat it like my baby, oil changes every 3 months, at 21,000 miles had all the fluids changed, etc. When I start it up, I run it for about 2-3 minutes to warm it up in cold weather. But in July 2010 it started giving me problems starting up and the mechanic diagnosed the Mass Air Flow Sensor which he replaced (TWICE). Then it started stalling out at red lights, when I stopped and sometimes it took me 20 minutes for the MAF to kick in so the car could drive. I took it to another mechanic who had to do a rewiring of the MAF after the Engine Light came on with a code. Now it starts up great under any weather conditions, hot or cold. IT RAN OK FOR ABOUT A MONTH BUT RECENTLY IT INTERMITTANTLY STALLED AT A STOP SIGN OR A RED LIGHT, STUMBLES AND DRIVES ROUGH, HAS LOW ACCELERATION AND LOW POWER. THIS HAPPENS INTERMITTANTLY. THE MECHANIC RAN A VALIDATION TEST AND DROVE IT FOR ABOUT 10 MILES AND FOUND NO PROBLEMS WITH IT. IT REALLY DRIVES A LITTLE ROUGH IN STOP & GO TRAFFIC. ON THE HIGHWAY AT ABOUT 50 MPH, ITS NOT BAD. I'VE BEEN DEALING WITH THIS FOR 7 MONTHS AND SPENT APPROX. $1200 ON REPAIRS. I'VE BEEN THINKING OF TRADING IT IN FOR ANOTHER SUV BUT MY SON AND THE MECHANIC TELL ME NOT TO DO IT BECAUSE OF THE LOW MILEAGE AND THE GREAT CONDITION ITS IN, EXCEPT FOR THE MAF. THE MECHANIC TOLD ME TODAY HE CANNOT KEEP GUESSING ON THE PROBLEM. THE STALLING HAS TO OCCUR MORE FREQUENTLY SO HE CAN DIAGONOSE THE PROBLEM AND DEAL WITH IT. I FEEL VERY NERVOUS DRIVING THE SUV AND I WISH IT WERE BACK BEFORE THE MAF PROBLEMS. WHAT COULD IT BE? HELP. NEED A CAR I CAN DEPEND ON.