[Kahuna]

There is no question in my mind it is the engine. I just went thru this about 6 months ago on an engine that I had invested a LOT of money in. Virtually all the machine work had to be redone. When finished, the NEW machinist (John Beck, Pro Machine in Chico), who did all the RE machining, called and asked if the engine had run smoothly before. I said NO, that it did not. He said the crank was out of balance 110 grams.
That's a lot of weight.
Sorry, Henry, I don't see an easy or inexpensive fix
Jim