At a WetWesties gathering last weekend there were two vehicles that were
having some problems.  One was expecting to replace a throttle cable, maybe
even on the trip home.  The other Vanagon would start and run for a couple
of minutes but was having great problems keeping running after that.  The
owners had an appointment to have the AFM replaced to try to cure the
problem.  But we had in out group the Wizzard of Walla Walla, a top VW
(actually any European vehicle) mechanic.  And he took a look at both.  The
throttle cable problem was cured by repositioning a spring to the right
anchor point.  And the hard running problem was a cracked crankcase breather
tower, temp fix with duct tape.
Both problems had been looked at by good, experienced mechanics, one by the
owner and one by mechanics at a shop with a very good reputation.  But the
experience and understanding and familiararity with the vehicle found, in
very short order, the true problem.
So, if you are like me and depend on someone else to troubleshoot and
maintain your engine compartment AND you have a REALLY good mechanic treat
him (or her) very, very well.
BTW you have noticed that I didn't give the name of the Wizzard of Walla
Walla.  That's because I don't know whether he wants to be deluged with
requests for work or not.