Doug:

Check your valves again. If they were tight, they probably had considerable carbon buildup on them, and when you adjusted them and the compression came up, it burned off, leaving you with tight valves again. This can happen pretty quick! It did to me -- within a few thousand miles I only had 0.005" clearance on #1 exhaust.

If that doesn't fix the smoke, it's time for a compression/leakdown test and injector check. Bad injectors will produce excessive smoke at idle, rough running, poor power, etc. So will uneven or low compression from worn cylinder walls or bad valves.

What is you oil consumption like?

At 200,000 miles a valve job may be in order, especially if you have symptoms of leaking valve guide seals.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!