I had a new tb installed on my 03 g35 a few days ago, all relearns completed successfully and then the following day the car went back in limp mode, relearns redone and once again, the very same night, limp mode after tge car had sat for a couple hours, now the relearns aren't working and the car won't come out of limp mode, codes present: p1122, p1126, p0507

 

Was it an oem throttle body? That's a part that I'd stick with oem. You can try cleaning the MAF sensor

 

I'd troubleshoot the throttle control actuator. It's the existing one right? Did you move the throttle plate AT ALL with the actuator attached? It's very easily damaged if you try to work the butterfly by hand.