Todd, I re-read your first post, does your motor sputter before it dies? Can you apply the choke to keep it running at 3000+ rpm? )This dumps raw unmixed gas into the engine, but in your case since they mixed gas and oil in the tank it would be ok to try a few times for test purposes.) Are you hitting 3000 rpm in gear or in idle (eng load) We were able to hit normal rpm in neutral but when in gear it wouldn't go above 3-3500 then spit and sputtered like crazy, had to use the choke trick once in a while to get home. Good luck with the trouble shooting. If your going to pull the carbs off, make sure to not change the mixture screws. I'm leaning toward a bad batch of gas and now you have some water in the carbs, but that's just me. Look at your tank vent, maybe clogged
Eric