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.

__________________
DS
2010 CL550 - Heaven help me but it's beautiful
87 300D a labor of love
11 GLK 350 So far, so good
08 E350 4matic, Love it.
99 E320 too rusted, sold
87 260E Donated to Newgate School
www.Newgateschool.org - check it out.
12 Ford Escape, sold, forgotten
87 300D, sold, what a mistake
06 Passat 2.0T, PITA, sold

Las Vegas NV