The tan sleeves are to protect the fuel hose from abrasion.I think they are
the same as used for electrical wiring harneses on the Vanagon. I had
difficulty getting the new fuel lines to go through them. Soap did the
trick.Also,I think that the OEM routing allows for preheating of the
fuel,buy the warm block.It does take a few minutes for the volume inside
the lines to get to the injectors.Gas in the tank can be very cold and wont
vaporize as quickly.Use fuel injection clamps!