Cummins N14 boosting the power/filter vac #'s

I have a 'new to me' truck with an N14 Cummins that is supposed to be built to 500HP but is in reality an absolute dog even with 30LBS of boost on the gauge. 300,000 miles on an out of frame which included new heads, turbo, injectors, fuel pump, manifolds etc with paperwork to prove it.

I NEED to get more power out of this engine, as I am being passed by old overloaded Autocar dump trucks on the hills. What can be done to wake it up? It's a 91 Pete with the Cummins N14 Celect.

Before I have somebody plug into the truck I'm curious how big of an effect would high #'s on the filter vacuum gauge have on performance? 10LBS vacuum at idle and 15-20 while driving. It spikes the highest while coasting, decelerating or using the jakes which pegs the needle.

I've narrowed down the root cause of the high #'s to the fuel lines, somebody installed too narrow of a line between the tank and ECM cooler. The numbers are much lower(2LBS total) if I go direct from the filter to the tank.

Working on getting new lines built and installing some sort of pre filter. On a total side note are the FASS systems worth it?

 

I should have been a little more clear, the high #'s are on the fuel filter gauge. Air filter #'s are fine.

For ####s and grins I'll replace the air filter to see if it improves anything, no clue how old it is anyway.

 

Fuel vacuum.