Just a quick contribution to this CEL thread. It seems that my 99 320 has had this malfunction light on for about 75% of the time since it was a year old. Four different shops have read then cleared the codes but the light always came back on within a week. At different times I've been told that the MAS or the purge valve may have been at fault. Codes reported to me include: PO300, 301, 130, 135, 170, 173, 302, 303, 442.

The purge valve was replaced about two years ago but the CEL was not out for long. Last summer when the MAS signal was again reported out of range, it ws changed. Following replacement of the MAS, the light stayed out -- for about a hundred miles.

In all this time, the vehicle has only stumbled once (while trying to pass a truck about two years ago). Otherwise, the engine has responded well and still sounds as smooth as the day of purchase. Gas mileage seems reasonable (but I should formally check it). Although I was originally concerned about the CEL being on, I've just learned to live with it. The shops involved haven't conveyed any urgency so no sense in loosing sleep.