The two stroke EZ Gos dont like exhaust leaks very much and it will run optimally with that sealed up. It may also fix your other problems. Replacing the belt is good, that the most common cause of slipping so you eliminated that possibility. The old clutch could be worn out but you will know more when you seal up the exhaust. So do that first and then get back to us on the power loss and backfiring. That simple gasket may wind up fixing all of it. If it doesnt fix the backfire, that will be an easy fix. The power loss may get a little more complex. On that fuel, just make sure you are mixing 128:1. Ive seen a lot of people who run 50:1 because thats a common ratio for two strokes, but the EZ Go wont like it
