Hi all,
Well, it's over a year later, but I finally fixed the problem today. The cause was... (drumroll please) ... the valve seals. I had to buy the SirTools valve spring tool so I could do the work myself (why oh WHY can't they give a simple instruction sheet with tools that are designed to work on multiple engines!? Idiots!) which cost ~$200 from IMPCO, the cheapest I could locate. What I found was the number 4 exhaust seal was not seated! The other 11 seals required work to yank off with pliers. Another point was when the new head was assembled at the machine shop, I gave them aftermarket seals (not knowing the OE were different). Seems that those were the old type, and MB has since rolled them to a newer Viton material with metal base (see photos below). So while I was in there I replaced all the seals with the new genuine Mercedes seal kit, which costs 3 times as much as aftermarket. AND, the OE kit came with plastic installation tubes! This prevents the seal lip from getting damaged by the keeper groove at the top of the valve stem. I bet the machine shop didn't use anything when they installed my aftermarket ones.
Anyway, I'll spare y'all the details of the procedure (which was filled with drama), but the result is a smoke-free car! I can let it idle for several minutes now, blip the throttle, and get ZERO smoke!
I haven't checked the leak but I assume it is also cured (need to clean off the block so I can tell, right now it's oily & filthy.) Now as long as my oil consumption goes back to normal I'm all set - woo-hoo! Oil consumption was roughly 7500 miles per quart with the old head, and dropped to ~4000 miles per quart with the new head (and improperly installed seals). See photos below. Just wanted to share the final resolution...
Regards,