Hi,

Did you manage to resolve this? i'm experiencing the exact same thing at the moment. I have tried everything that you have above, and nothing obvious, i also checked the error codes coming from the ECU, and it was saying that there was an error with the speed sensor. I have tried replacing this but to no avail as of yet.

Only other thing i can think to try is a new guage cluster to see if that resolves the issue, but they can be fairly expensive, and then you have the issue that it will display the wrong mileage.