On my '99 E300 turbodiesel (606 engine) there is a clearish fuel hose, hard/stiff plastic, that goes between the fuel filter to the actuator. Basically the clear plastic fuel hose going from the fuel filter back toward the injection pump. Anyone know what size fuel tubing this is or the material?? Thanks much. The hoses im referring to look yellow in the pic due to the wonderful biodiesel fuel!