This winter my 1986 300SDL w/320k original miles has no power until it reaches operating temperature (80 degrees celsius on the dash guage). It starts great, idles perfectly and sounds like all 6 cylinders are firing properly at idle and during acceleration. But it feels as if I'm towing a barge (takes a lot of pedal to get her down the road and top speed going downhill is about 65mph). On really cold days I can go about 2 - 3 miles like this until she hits a little above 80 degrees celsius. When she reaches operating temperature she feels like she just got shot out of a slinghot. Then she'll run 100mph all day long without a problem. When she's warm she'll re-start and run fine. And, on warm winter days, it only takes about a mile for the problem to clear. I've replaced both fuel filters and I run diesel fuel additives every other tankful or so. She feels like she's not getting air... Is something preventing the turbo from spinning up till it gets warm? Fuel preheater problem? Thanks in advance!