Originally Posted by Mitch H

Extremely common upgrade on 12v Cummins 6BT in Dodge pickups. AFAIK, less fuel spills to the return line and more goes into the combustion chamber. Delivery valves on P7100 pumps are another common Dodge upgrade.

I can tell you that several 400hp+ 603s are running around europe with the original injectors and delivery valves. (they replace the 5.5mm pump elements with 7mm and other pump mods, along with intercoolers, custom manifolds and big turbos (like Holset HX40W).
I'm thinking of taking a similar course with my OM602. I won't do a whole lot to the pump, just put the 7mm plungers & barrels in and modify the governor to start defueling at 6000rpm. I'll probably use a Garrett GT23 VNT, which is between the size of the stock turbo and a Holset HX35, should be good for 250-275hp, with less turbo lag than a Holset or even a stock turbo.

Warning:
I would not do anything to increase fueling beyond stock, or increase boost beyond 15psi, without a good exhaust gas temperature gauge. A MBZ turbo properly set to stock specs is already capable of some scary exhaust temp numbers. A turn or two on the full load stop screw could probably get you a cracked head or piston if you aren't careful. You will almost certainly need an intercooler to get a noticeable power increase without meltdown.