Is it large amounts of oil, or just wet? Both my 94 E320 and my 93 300E (both M104s) have a little oil in the intake, but don't burn any and the plugs look good.
I've always been confused as to why Mercedes didn't put the crankcase vents further up the sides of the crossover duct or put a filter in that area to keep that oil in the crankcase where it belongs. If it's not much, don't worry about it.