from your previous posts.... it sounds like Emily is one bad girl.....

Any chance you can try a code reader, and see if anything shows up there?

I'm pretty new at diesels, but... (I'm ase certified, and have a few hours around cars)

There is an 02 sensor or something like it on these cars. It sounds to me when it goes 'closed loop' (if there is such a thing for diesels) that the mixture is off.

MAF?
silly as it sounds... air cleaner?
time to go for a good highway run and blow it out?.
fuel? (siphon what is there, and replace it with fresh)
Maybe it's time for a diesel purge?

Anyways... My dime's worth.

For what it's worth... I've had my MY99 E300 for a year. 24K miles. Oil changes, filters, and glow plugs. 72K and counting....

Jnc...

99 E300
99 Boxster
03 S type.
70 914/6.