Roy I have the same engine, only in an 01 Diplomat. That plug you found is not an OBD11 plug. True that plug does have data available, but not for a ScanGauge. You can purchase a VMSpc device and cable that will connect to that plug. The plug will be either a 6 or 9 pin and you need to order the correct plug from the folks at Silverleaf. Check out their web site
http://www.silverleafelectronics.com/?q=forum/23
There you may also download FREE their VMSpc software for use on your computer. The VMSpc unit connects to the serial port of a computer, but can also be connected via USB with the appropriate drivers.
With this device and software, you can view all the engine data, and some transmission data. The software is easy to use and is much more accurate that the instrument panel in your coach.