[Booker42]

check this out...if its an earlier 986 you just need an odometer adjustment...no board changes or even programming necessary:

https://www.pelicanparts.com/techarticles/Boxster_Tech/90-ELEC-996_Cluster/90-ELEC-996_Cluster.htm

odo adjust at Palo Alto Speedometer

Palo Alto Speedometer: Repair, Restoration, and Sales of Automobile Gauges