I've got a 94 E320 and I am trying to chase down an intermittent (warm motor) idle surge problem that began yesterday.

Here are the fault codes:

DM (built-in) Code 4 - Air inj. sys. faulty hot film mass air flow sensor with hot wire (I've had this for months)

PIN 8 Code 13 O2S (Lambda) control sys. operating at rich or lean limit

PIN 14 Code 14 Closed throttle position contact switch.
Code 5 Stop lamp switch (stop lamp works though)


Some notes: The problem began yesterday. It's been pretty dusty and cold here in the northeast, I've yet to clean the throttle linkage. I'm confused by the Code 4 from the DM (built-in), Is it 1. the Air Inj. sys. OR 2, the MAF sensor? I've had that code for a while. Past posts on the subject call for a replacement of the MAF with some success, so I'm looking for some opinions before a MAF becomes birthday present for myself, whether I really need it or not

Any thoughts?

Thanks
Geoff