Head gasket or something entirely different

07 f-350 6.0

I have the arp head studs installed and its got a lot of pressure in the bottle, like 24 psi. Ford said head gaskets, good diesel mech friend said something along the lines of o rings around the water jackets around the injectors are probably bad and letting pressure by into the bottle.. Is this complete bs? His price to fix that compared to fords head gasket replacement sure sounds better but his diagnosis sounds a bit off.

is egr system deleted? i suppose the injector cups could be cracked and allowing combustion to enter the cooling system. need a little more info, how long ago was it studded, were the heads pulled, what gaskets were used if the heads were pulled? and where are you located. me and my father run a diesel shop and work on many 6.0's in SW missouri. Not sure what part of arkansas you were from.

what kind of head gaskets were used when it was studed?