This may sound stupid, and I don't want to insult you or anything. I just know how easy it can be to overlook something when you are frustrated. When you say it sounds like a dirt bike, that makes me think missing/timing problem. I would have you unplug your spout connector, clean it with electrical cleaner, and make sure it is plugged fully together. If it isn't making good contact, that would screw with your timing advance, maybe cause your rough running, tach symptoms, and trip the spout code you mentioned. At any rate, it won't cost anything to check it. Good luck.