A cross section is cut away to reveal the lubrication port for the "Direct Loss" oil lubrication to the Piston & Plunger section of the pump. I guess I should expand on this just a little. On the street MFI Engines the Injection pump has engine oil pumped thru it to lubricate the pump and all of its internal parts. On the competition engines the pump has it's own oil supply in the body that needs to be checked periodically and the rack has a dead head oil pressure port to lubricate the pistons and plungers. This oil is burned in the combustion chamber thus the term "Direct Loss".
The reason for this is so the fuel cannot dilute the engine oil and thin it causing obvious hardships for the engine.