you mentioned that disconnecting the MAF improved drivability, this is pretty much a given for a failing MAF but some points are also to be considered - air leak at the throttle body etc.

the 4.3 litre V8 is like a 3.2 litre V6 with 2 added cylinders, these engines have a peculiar breather system which is plumbed from both valve covers and any leaks there also cause low MAF signal.

Whilst at it - perform a throttle pedal sync, It helped me in one very odd problem my car had, it would kickdown at even 30% throttle input and hold onto a gear even at full rpm redline which caused it to record a misfire code. The sync solved it.

It would also be wise to have your car scanned on a STAR diagnosis system and test the gear selector itself for all shift ranges and the S/W switch operation.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)