I have a 2012 People 150 with the same problem, it started a week after I have new tirs mounted at the Kymco dealer. I replace the gasket with no lasting effect, it started leaking again after about two weeks. I removed the exhaust and looked at the gasket ring and it still looked new. My fix, let the darn thing leak a little, doesn't bother me. I have 18000 klm on my unit waiting for the spring thaw.