Posted for "Jim Rogers" <n360jr@adelphia.net>:

 With regard to the detonation problem, I can only say that my experience with
high flyers has been that without the correct pressurization of the mags,
harnesses that are not completely up to snuff and spark plug gap not set at
the proper setting for high altitude,you will experience this problem. I
believe that contacting the magneto guys would be better than continental.
When setting the plug gap, it will be different at high altitude than for the
low level guys. Check the lead ends for discolorization. If it is there, clean
it up. It will lead to bad firing and unburnt fuel.  Jim