I believe you can turn the pumps up a lil on them.
On your 7.3 you can make it a lil quieter and make a lil more power. The oil that feeds the injectors hits a dead end in the back of the head. There is a plug that can be removed and they sell a crossover line that you thread in that connects one head to the other. Only buy the steel braided kind though. It balances out the injector oil preasure and quiets them down. Also there is a fuel tank mod you can do as well. Requires removal of the tank to trim the return spout. This keeps from getting hot airiated fuel back to the motor. Or you can put an airdog or fass system on it. The 6.slow lol you mentioned is great with a programmer and simple mods though once he starts making good boost I would suggest head studs and good head gaskets. Believe we had the one guys 6.0 running low 13’s high 12’s.