Well, if it were my sohc(different carbs though), I would check if my ignition pickups are set right. I don't know the dohc ignition, though. But many ignition problems don't show up till higher rpm. Honestly, your charging system really shouldn't matter as these bikes should run fine as a total loss system till the battery drains too much. The manual should describe some ignition tests that can be performed to make sure things are firing right at higher rpm.
I would also attempt a high speed plug chop. Bogging down like that can be a sign of not enough fuel. Your fuel goes through more than 1 jet at that throttle position.
Also, check float levels. A level that might be fine for lower rpm, might not be for higher rpm. Many people goof when setting float height. Best way to do it is to turn the carb just enough so that the float closes the needle valve, but not so much that the little pin in the needle valve gets pressed in. About a 45 degree angle is optimal, so turn the carbs upside down, with floats up. Then turn to about 45 degrees and the needle should be closed but the little pin in the needle should not be pressed in.
Then, do not measure from the from edge of the float, measure from the side of the float, in the middle. Low float measurement means more fuel in the bowl, higher means less. When you turn the carbs right side up, you'll see what I mean.
From there, you need to make sure the bowls do fill properly. Hook clear tubing onto the drain nipples and then open the screws. The fuel will rise to the same height as the fuel in the bowl. All 4 should be about even. This is a bit of a pain with the vacuum petcocks but it can be done.
I don't see why you would think a head gasket issue. If you don't have oil leaking out, the gasket should be fine. If in question, do a compression check with a gauge that can read motorcycles. Larger auto gauges do not always read smaller engine pressures, properly.
The ride IS the adventure. The destination is just to get gas!