I really would appreciate some help on this problem. I have 1997 Mercedes E300 naturally aspirated diesel. In the mornings when engine is cold it misses on one or two cylinders till it warms up about 5-10 minutes. It's not a fuel issue. I did the paper-over-tailpipe test and indeed it is sucking in during misfire. My current theory is lifters that won't squeeze down enough and is holding open the valves open. Could it be the valve itself is just sticking open because of sticky carbon deposits on shaft holding it open. I have been running WVO in this car and it makes no difference in the symptoms even when I switch back to straight diesel. It gets a little better on a fresh oil-change and 25 oz of stiction eliminator oil additive. Thanks Tyson