The engine starts with no issue immediately revs to 2000rpm the sputters down to idling speed and then stalls out. It’ll stay going if I keep the throttle open after starting until it is warm once warm it will idle smooth And drive but will have some kind of power lag while driving too.

Any my help will be great as I’ve just been chasing mistakes from the previous owner. And this is my last problem to get the truck running

 

Try changing out or cleaning the IAC valve that should help with your high idle and stalling. For the loss of power while driving im thinking its either air or fuel related but I'm not a mechanic