14L Detroit Oil loss or Consumption problem

Aight so i rebuilt this engine just over 75k miles ago. Truck been running solid since it's first trip otr, mpg between 4.5 - 5.8 loaded performance isn't a problem here. My issue here is that this truck has been loosing oil since the start (about 1gal/800 miles) , im aware of the break in process and that oil consumption is normal on a fresh rebuilt engine, but at over 75k miles the consumption is the same and im starting to get a lil concerned here. I have replaced the head (reman) and replaced 2 air compressors. I'm told to replace the turbo but it doesn't make sense to replace it since both cold and hot sides are dry. I even plumbed a manometer to the crankcase via oil dip stick to measure pressure and it reads 2in H²O at cruise and 3in H²O going up hills at 1800rpm (LOADED). Any input and suggestions is greatly appreciated. Thank you

 

I use T6 Rotella 15/40, aftermarket kit from ATL DIESEL, supposedly a reputable machine shop. No oil analysis yet but will get it soon

 

Large ring gap would make sense, but wouldn't that cause excessive crankcase pressure too? Considering my egr is deleted the oil does get black fairly quickly after oil changes.