Sounds like an air availability problem. Maybe opening the airbox, removing its snorkels, modifying/opening the exhaust mufflers, and rejetting the carbs would help. These are inexpensive mods, but quite effective. Check the tech vault for particulars. There is a good website that "Dinqua" (Pat) (Dinqua.com)has with pictures about this kind of stuff, with the link in the tech vault:
http://www.bonnevilleamerica.com/forums/...age=0#Post89123
