I think you mentioned you were getting a gradual increase in crankcase oil
level over time?
ON EDIT: I checked back and found that I'd misread: you were losing oil, presumably by the bypass from the rocker box to the intake, so disregard the following:
I'm sure you've considered that you might
be seeing the symptoms of more than one problem at a time, but I'm just dropping this into the mix for the benefit of anyone who might stumble across this, who assumes that when they have an evident engine
problem, the symptoms will all be related to that problem.
For example, engines like this with a direct-mounted fuel pump
can develop a small hole in the diaphragm
which will allow a small quantity of diesel
to leak directly into the crankcase, sometimes just the right amount to cancel the decline in oil level, but sometimes more than enough.
This is definitely Not A Good Thing. (diesel oil is NOT a lubricant, at least, not for bottom ends and bores...)
Worth thinking about anytime a rebuild
is undertaken, for one thing ...