STALLS AT PART THROTTLE

CAN ANYONE TELL ME IF THEY HAVE HAD THIS PROBLEM WITH THEIR CAR OR ANY HELP ON THIS. I HAVE A 2000 GT WITH FULL LENGTH HEADERS OFF ROAD H-PIPE 410 GEARS A DIABLOSPORT TUNER. THE CAR IS SELF WILL RUN PERFECT AT FULL
THROTTLE OR MID THROTTLE BUT AT PART THROTTLE THE CAR FEELS LIKE IT IS GETTING NO GAS THEN GIVE IT GAS AND IT TAKES OFF I HAVE HAD IT AT THE FORD HOUSE THEY SAID IT WAS REAR O2 SENSORS.I TURNED THOSE SENSORS OFF ECT. SAME PROBLEM. CODE SCANNER AT PARTS HOUSE SAYS SENSORS ARE READING RICH AND LEAN ATTHE SAME TIME ANY HELP THANKS