with this type of engine and that many miles, I suspect that you are drowning your exhaust valve stems in oil while braking for a corner, if you are driving quite aggressively, and the valve stem seals are no longer up to the task. Have you ever seen an old V12 Ferrari blow smoke after every corner? (I used to see it a lot at Brainerd International 30 years ago when I was a corner worker and lived in Royalton) The design of that motor put the exhaust valve stems under oil anytime the car wasn't accelerating and they sucked it in like crazy under engine braking.

Basically, the question comes down to this: are you losing anti-freeze? If not it's probably oil going past the valve stems.