Had this problem ever since I installed the phearable 70mm throttle body. At first it was just idle'ing low, but now every time I go to start the vehicle, hot or cold, it will stall unless I keep my foot on the throttle. Once I get going though it won't stall until I shut it off and try re-starting the vehicle. Thoughts?

 

Have you cleaned the IACV and adjusted the idle speed?

CEL codes?

 

Reinstall old TPS onto new TB? Then recalibrate the TPS. If none of the above? Retune for the TB. You just introduced more airflow into the system and should do so anyway.