Very interesting that this does not show up in the leak-down test. I was pretty sure that your valve guides are not warn but this assertion at least fits the original assessment of the shop. Top and bottom ends not matching...Hmmm. Compression of >200PSI sounds high to me but that must be normal for a brand new valve job. I also have a couple of questions to you both:
(1) Is there a way to definitely prove this is the case?
(2) Stardivari, what type and viscocity oil are you using? I suspect synthetics would be worse for this but certainly a viscocity of 20W50 may help in your case. That is what I use in my M103, 20W50 conventional.
The shop that did the work reported compression of ~180psi across all cylinders. The data obtained yesterday were from a third party shop, now approximately 300 miles since the plugs were changed. He said that when he pulled the plugs there was no sign of fouling but did note the white smoke from the tailpipe. He didn't rule out that the bottom end could be contributing to the matter but at the same time felt that the oil consumption was excessive given the test results.
The car was put on 5/30 synthetic when the rebuild was done. I tried switching to 20/50 conventional around 5000 miles and it doesn't seem to make much, if any, difference.
One observation I've noticed is that the rate of consumption doesn't seem to be consistent through the 500 mile period. It will surely burn a quart every 500 miles, but sometimes no consumption is seen for the first 2 or 300 miles (and every time I see that I think, "ooh, maybe it's stopped") and then the consumption progresses rapidly over the next couple of hundred miles.