if it had problems before it rained, the rain wouldn't have anything to do with the trouble..
bogging at high speed could be caused by lots of things.. ignition problems due to screwed up wiring.. fuel delivery or carburation are always strong suspects. Fuel or air or vacuum leaks .. a loose nut or bolt or wiring connection.
Since the trouble appears and then disappears it's probably something very simple that a close inspection, cleaning and tuneup would cure. Take a day off and get everything straightened out.