Courtesy of Sho968, Here is the Wiring Diagram with Instructions on where to connnect:
To tap the Speed Sensor Wire for your Nav system, remove the Instrument Cluster and find Connector "B" (the middle one)
Find the Red/Black wire and splice into it - Connect this to the Speed Sensor Wire of your Nav System (usually Pink)
94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating
www.968forums.com
"It isn't nearly as expensive to do it right as it is to do it wrong."