I suspect that your mechanic moved the distributor timing setting to change
the hoses.When he set it back,he did it manually ,without using a timing
light. Tell you what to do.Remove the engine hatch cover and drive up a
steep hill.Are you getting lots of pinging,or predetenation from the
engine? Your timing is way off.Is power from the engine different from
before? This ignition timing change also causes bad gas mileage. May not as
basd as you are getting,though.

As for the fuel injection hose  clamps. That is the only way to go.Hose
clamps grind an cut their way into rubber hoses,over time.

As for replacing fuel hoses.only use fuel line.It is pressure rated for
high jpressure that fuelinjectores need.Old carburated engines had fuel
pressure of 6 or 7 psi,at most. Fuel injection needs 29psi ,in the Vanagon.

As for replacing origional fuel hoses.Mine have lasted for 22 years.If I
replace them,the new ones will only last a year or two.I have seen new
rubber  hoses go bad too often.My opinion.