Yamaha Excel misfiring ???

[Fishsticker]

I have a 1989 Yamaha Excel that seems to be misfiring all 6 cylinders.While running at low idle speed it will kill the engine, and at cruising speed it feels if you have hit something solid then picks right back up and runs fine. This has been very spuratic sometimes multiple times sometimes hours between stalls?I have looked in the clymers manual and its states the computer will misfre all 6 if it detects a shift from forward to reverse at high rpm.Is there a switch in the control box that could cause this?One other thing i have tried is disconnecting the thermosensor which seems to clear the problem,however whenever I replaced it with a new one the trouble remained so apparentley that was not it.