Electrosport does make a slightly higher output atlernator:
http://www.electrosport.com/
I don't have the nominal engine management power usage, but would suggest getting a voltage meter of sorts to monitor your battery's condition. I like these:
http://www.aerostich.com/catalog/US/...r-p-16951.html
You can get something similar for much cheaper at any auto parts store. With a meter of this type, you can 'watch' and see how much drain is occuring on your battery. Too much drain, turn something off. I, too, use heated grips, and a heated jacket, along with a GPS - and haven't had any trouble. Only one heated jacket though.
Good luck.
