D13 Oil pressure drop while accelerating under load or when Jake brakes are applied

It's a 2013 D13 with 600k. Started noticing this fenomena few months ago but lately it became more apparent. Someone told me that some sort of seal or o-ring where oil supply connects to Jake brakes tends to leak oil out therefore lowering the pressure in the system. It's most noticeable when running at highway speed while loaded and accelerating hard, I can probably see 5-10psi drop in oil pressure. Do you have any advice on how to tackle this? I know that D16 has a oil pressure relief valve mounted in the oil filter housing that can cause low oil pressure not sure about D13 however, Thanks in advance