Stored code 2215

[Rex012]

So after doing a little digging on my truck it had a stored code of 2215. (Found a pictures of stored codes before Cummins cleared them) Which is the delivery pressure is low. My truck has a weak idle and the truck feels weak I have done the cylinder out test and all injectors seem fine and so do the actualors (turn off first 3 cylinders then the other half) the engine still runs. My fuel pressure at idle is like 268 psi. Any tips to help this mystery will be greatly appreciated. Thanks in advance guys