Ok, for all those 1997-99 E300dMB owners experiencing hesitation and suspect o-rings, air in fuel lines, k-40 relays, egr sensors as source of the problem but are frustrated to find out that it isn't, try cleaning your gas tank. I did all the above only to find out that my gas tank was so dirty that muck has covered much of the fuel filter located inside the gas tank. I replaced again the fuel filter in the engine and had the tank removed and cleaned. It is now running so smooth as though it was brand new. It is frustrating that MB bulletins do not indicate this as a potential problem.