Well without any noticeable problem such as smoke, rise in temperature, loss of power or hard starting I've decided to change the mixing elbow after 15 years of service and maybe 1700 (+,-) engine hours. I put the work order in today as a winter maintenance issue that's been on my mind. Does anyone know what the factory suggested time for swap-out is and what the estimated cost will be. My yard says about 2 hours labor and the part itself.