If you're puking old dipsticks out have you done the suck and blow test at the vents on the heads? Maybe some old cylinder head breathers not up to par anymore?
It's pretty much been an issue since I had the dealer repair bent valves under warranty (guide drop).
I never beat on the bike much so it did not immediately become a problem. I thought I found the cause when I removed the cylinders several years ago and found the winning lottery ticket of all 5 ring gaps lined up (you probably remember that).
Since then the cams were changed, new cylinders and heads of which John S worked over before I put them on. Breathers were new at that time and sometime later they were removed and replaced a second time. Very rare this bike sees above 5K or has WOT pulls.
There are other things I've tried along the way that I have forgotten as well.