e34 instrument cluster & idle questions

[Jimmy Pang <jimmyp@xxxxxxxxxxxxxx>]

Hi all.
I've been holding off asking this for a long time, hoping I could find
another way to resolve my problems, but I'm now ready for answers. Hope
someone knows them.

Question 1: Can I replace my current instrument cluster (analog trip and
odometer on a 89 5 series) to the digital one on a 90-91 e34. I believe
(perhaps wrongly) that the 90-91 is also a m20 engine. Are the connectors
different?

Question 2: When idling, the engine tends to stumble a little occasionally,
and there is this mild surging (a kind of gentle regular shoving of the car
forward when you release the brake pedal and the auto trans creeps forward.
The tacho doesnt seem to register any change engine speed though) that is
periodic with a cycle time of about 1 second (1 Hz). I'm told that
cylinders 5 and 6 have low compression. Is that symptomatic of the bad
compression on 5 and 6, or am I probably looking at a sticky idle control
valve?

Question 3. Is the typical carbon deposit problem usually with the intake
or exhaust valves? Or is there no general 'trend'. Would injector cleaners
usually help much in these cases? I'm told the compression on 5 and 6 are
lower when the engine is cold and better when the engine is warm, but the
surging seems to start after the engine warms up.

Sorry for the long questions. I'm sure someone on this list knows the
answers. Thanks

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