Truck originally had a bad lifter noise and customer tought it needed an engine it ran rough miss under load. Fixed the noise by installing a new cam and timing set due to lobes being 30 thousance diffrence and the chain having slop in it. Now that everything is back together it takes a few min for it to fire. It also falls on its face under any kind of load. It only idles once the engine warms up. I'm really not sure were else to go from here. Any help would be nice.