Code P2138 will not go away?

This code has been popping up for the longest time now, it’s been about 3 months and I've done everything possible; I've had the throttle body changed 2 times and I've changed the pedal more than 3 times. I took it into a shop to get checked out and they said they checked the wiring and everything else and they said it was fine so I brought it back home and tried to reset the ECM and it worked but, when I turned the car on and revved the engine the check engine light would come right back on same with the ‘power reduced’ engine light. I've tried everything and I really don’t know what else to do I really want to get this problem solved before September.