The car has been running beautifully for a number of years and then all of a sudden it started to stall at tickover and has a very rough idle. It starts first twist of the key hot or cold and after the air pump stops the idle becomes rough and finally stalls. It also accasionally appears to shut down for a couple of seconds when cruising with around 2000 or less rpm.
I made the code reader and got the following codes from the 16pin diagnostic module.
Pin 8
code 3 air intake temp sensor
code 4 hot film mass air flow sensor
code 13 O2S(lambda) control operating at rich or lean limit

Pin 14
Code 2 Cruise control/idle speed control module
Code 5 stop lamp switch
Code 11 fuel safety shut-off to LF-SFI control module

I have over the past couple of years replaced the wiring loom and the throttle module, cruise control works fine (throttle module hums with ignition on ?). Plugs and coils are fine. I have never looked at or cleaned the EGR valve and pipework. The EGR diaphram appears to be ok as I can actuate it by sucking on the vacuum line, there is no vacuum on this line at idle (is this correct).

My question is where do I start to chase this problem down. Is there anything I should try first or is there further tests I need to do before I start to replace things. You help wold be appreciated.

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1993 320E 140,000km