I own a 1994 Toyota camry 2dr coupe with the 1mzf 3.0 litre engine. I had to have the engine rebuilt due to a sludge build up problem common to these engines. The engine didn't run out of oil but the sludge build up blocked some of the oil passage ways and caused the engine to sieze up. After the enginge was rebuilt the car started to smoke on startup after it had sat for awhile. This was consistant with a valve stem seal problem and since they had used after market valve stem seal, I had them replaced with factory valve stem seals but this had no effect on the problem . The Toyota dealership couldn't figure out what the problem was, but after much frustration I was able to determine that the vacuum line with the pcv valve in it was sucking oil out of the valve cover and feeding it back into the combution chambre thus causing the car to smoke on startup. I have been able to stop this problem by making up an oil trap out of a water trap rom an airline from a copressor. If I empty the trap before it fills up, I'm able to keep the engine from smoking but I would like a better solution than this. I know my next option is to pull the valve cover and see if I can figure out why the oil is being sucked out by the vacuum line. There have been no changes to the valve cover except possibly some sludge build up in behind the baffles in the cover as the baffles were rivetted in the covers and I wasn't able to clean them thouroghly. I don't want to pull the cover just yet as it is a fairly time consuming job as it sits underneath the plennum at the back of the motor. We have also been able to determine by a leakdown test and no blow by that the rings have all seated properly. I would appreciate knowing if anybody out there has run into a similar problem or has any constructive ideas. Thankyou

See the articles linked at the bottom of this page:
http://www.yotarepair.com/Sludge_Zone.html

They believe there is no way to get away from replacing the valve cover.