Skip,

Don't overreact. The valve seal fix is not likely to be expensive as, since it was such a problem during the mid '80s, MB developed a procedure used by all the dealers where the job is done without taking the head off. The parts are a few bucks per seal (check Fastlane), and the labor is not a whole lot more than the change of valve springs or something that gets the camshaft out (maybe twice the hours for a valve adjustment on a W123). The previous owner of my 1988 300E had it done in Utah at a local independent MB service guy for under $130.

Even the prechambers are not likely to cost what you have already spent and they are much less likely, based on your description of the problem, to be the culprit. I hope I did not scare you as the intent was to let you know there is a potential solution other than tearing the engine apart, that was not likely to cost a fortune.

Keep the faith, the chances are your car is not suffering from a terminal malady. Good luck, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)