I have heard that the optimum jet is slightly rich at WOT and to tune this way. You should look for the engine speed to pick up at just slightly less than full open. This is a safety measure to ensure the longevity of the engine, especially if you find the majority of your riding is done at WOT. It does sound like you were running a bit rich for your preference, but be careful not to tune too lean! Your altitude may have amplified this more than would be at sea level also. A 118 may actually be ideal at sea level. Dropping 20 sizes is a huge difference, and I have a feeling you will be on the dangerous side if you do. I would try dropping 5 at a time, 10 at the most, and definitely get some extra plugs to do some reading!