Originally Posted by dlssmith

It works well to put the fitting in a vice with the barbs facing up and then heat the tube and fitting and push the tube down on the barbs. Should slide right on. I don't know if boiling (212 degree) water is hot enough. But a heat gun is if you apply the heat carefully and not get it hot enough to burn or become more than pliant. I believe the stiffness of the nylon is required to maintain the correct vacuum to the booster for the volume of vacuum spec'd. It would be too flexible to use a fuel hose or other rubber hose. Others here may know the exact reasons for the stiff nylon tube.