'94 Mack E7 427 Oil leaks

Hey guys, I have a CL613 n its got a leak. The best way to describe it is its a square shape box mounted to the front of the injector pump. There is some kinda solenoid bolted to the side of it with a guard plate over top of it. The leak is between the square box thing and the cast piece that its bolted to. What is this thing called? My local Mack dealer is of no help for trying to help me order the right gasket.

Also, is there anyway to get more TQ outa these engines without buying one of those generic power bixes? Ive called Pittsburg Power and a couple local ECM tuner guts n nobody seems to have any kinda upgrade for a Mack engine, even a proper one. I drive at 58 mph n pull a reefer n cant get more then 6 mpg...these were supposed to be fuel efficient engines...

 

I will get a pic when I stop in a couple hrs.

 

I wonder though if the generic power box is gonna change the fuel map enough to get me better fuel mileage, or just more power? It seems to be running rich now, clean air filter n no air to air leaks...but she can really roll coal when ya get on er. I wanna change that but not sure if the fuel pump is adjustable...