I believe there is an "altitude correction module" (my name) near the ECU behind the battery, but I can only give you an overview of why it's there and how it works. Most devices like this have a sealed chamber and a diaphagm that communicates with outside air. Movement of the diaphragm due to ambient pressure change is converted to some electric analog via strain gage or other means, which provides an electrical signal to the ECU that is an analog for ambient air pressure.

As you are probably aware the KE is a basic continuous flow mechanical FI system, and the O2 sensor and ECU provide continuous fine fuel flow calibration to maintan a stoichiometric A/F ratio via the EHA at all throttle settings other than WOT.

Since the altitude correction (higher altitudes require less fuel flow to maintain stoichiometric mixture due to less air density) is implemented through the EHA, disconnecting the altitude correction module may not make much difference as long as the O2 sensor is functional. My suspicion is that it is their to work with the system in the even of a failure somewhere in the electronic part of the system.

Back then Mercedes made a big deal out of the fact that the engine would still continue to operate in the event of a failure in the "E" part of the system, but the electronics have proved, over the years, to be fairly reliable.

I don't think most modern fuel systems have any kind of specific altitude correction. They just rely on the O2 sensor readings, and as air density varies, fuel flow is modified in real time to maintain stoich. At WOT a rich 12.5:1 A/F ratio is usually programmed in and is maintained because mass flow meters actually measure mass flow, so they automatically compensate for lower air density.

There is a lot of redundancy built into the KE system, but it's debatable whether it improves reliability or detracts from it because there is more hardware to break.

Depending on your perspective, the KE system is either an engineering marvel of a giant kluge.

An '86 300E with a five-speed is a rare and fine ride. My '88 190E 2.6 is also a five speed. They were only available on special order. It took four months for it to be delivered after I ordered it.

Duke