I have a '99 RX300 that will emit heavy smoke occasionally when it is first started after setting a while. The smoke looks like oil smoke, but it has a stronge chemical ordor. The valve covers have been removed and very little sludge was found. Two very capable mechanics are at a loss as to what is the cause. THe mileage is 130K and the timing belt,& water pump have been replaced. Has anyone had this experience?