Bummer, Andy! Sorry to see :(
And I agree, I don't think it has anything to do with Steve-O's tune. With the engine getting up there in age and mileage being pushed harder than normal, things are bound to go quicker. It was sorta like when I had to rebuild the head on mine. At over 400K km, valve stem seals were worn and one of the cylinders already had really low compression (especially compared to the rest), so I knew it was bound to go; I just didn't know when, so I continued to push it hard until it gave out. Now that it's rebuilt, it pulls harder than ever with the mods.
Looking forward to seeing where you go next with it, Andy! It'll be running better than ever once you've got it swapped.