Well, sometimes I just think about the most stupid thing it could be, and get lucky..
How about that maybe you have a leak in the lower radiator hose and the fan threw some coolant in a sparking thing..Like somehow getting inside the dizzy cap, coil wires or something like that...After all, the higher the RPM's, the faster the spark and would not be as effected with the moisture as it would at a lower RPM...
I think I would be looking for the wrong thing being wet..
Oh Well, I think I'll make a list of something I shouldn't forget..Whatever that might be..
Good Luck, Steve