Geg2rap:- Taxi speed only works on FS2002 AFAIK.
Beowulf:- What Geg2rap is talking about is a program that allows you to set the taxi speed to all of the AI
traffic. It is great for getting them off the runway faster after they have landed.
What you are talking about is a gauge that sets your taxi speed like an autopilot. There is one (dhc6_sw!Taxispd) that comes with the DH6 Skybus series of panels.