leaking coolant

[troyford417]

Ok, I bought a used 06 250 diesel with the 6L. It starts kinda rough and wont shift or accel right until its showing some temp on the gauge. Plus, when I floor it and the boost gauge goes over 20 psi, coolant runs out of
the tank. If I baby it, then it does not leak. I don't know much about diesels
so any help would be appreciated...

By the way, It still seams to have plenty of power.