I finally installed the new CP3 and the truck now hits desired rail pressure immediately. The pump was leak and on its way out!.
So now what I'm noticing is when you hold the brake and push the throttle to the floor the desired is only 6k and the truck does nothing. Also if you put the truck on a steep grade it will sit at 6k desired and not move or it will build desired pressure slowly and start to take off. This seems like if I would put a heavy trailer on it would do the same and would be dangerous. I'm not real familiar with Duramax but th