Here we go again. We just now got ms1/extra working on the NGC and the MS2/extra developers have added support for the NGC wheel. This is very early alpha test code. Realize that it will probably have bugs.
General info:
http://www.msextra.com/viewtopic.php?t=23867
Thread for testers:
http://www.msextra.com/viewtopic.php?t=24247
Advantages over MS1? 16-bit chip with much higher precision for both fuel and spark calcuations.
Cost? Extra $90. Simply unplug the ms1 cpu from your board and plug in the MS2. External wiring should be the same.