Volkswagen: another fuel-injected issue, air flow meter, vw pro

Question
Hi Ron!  I was fortunate enough to acquire a FREE '78 Super
Convert with the body in mint condition. I knew it wasn't
running, and ended up having the engine rebuilt by a local vw
pro.  

My little car ran GREAT until I had to get it smogged.  My life has
been a living hell ever since.  A different vw shop made the car
pass smog, and my original mechanic has turned himself inside
out trying to get things back to par.  

Here's what he's done: valve adjustment, timing adjustment, new
points, cap, rotor, wires (all Bosch), new ignition switch (the old
one needed wiggling to get it to turn over), replaced the air flow
meter (I forget exactly what it's called, but I think I'm right),
checked all the vac hoses, changed the air filter and inline fuel
filter, and readjusted the potentiometer. It'll run well
immediately after he makes any kind of adjustment, and then
once the car is fully warmed up, it starts running like ca-ca. It
runs extremely rich, backfires sometimes, has NO power,
hesitates when I hit the gas, stalls without warning.

I read your article on the 78 bus with similar problems, and
everything that you suggested troubleshooting, we did. It was
having problems with the cold start, but since we just replaced
the ignition switch, that problem seems to be resolved.  My
mechanic thinks that my problem is electrical, and as he is an
EXTREMELY well respected veedub guy, I believe him.  The
problem is, he's been trying to get my car running back to the
way it was after he rebuilt the engine, but to no avail.  I can see
that he's as frustrated as I am, and after asking several people,
rather than replace the computer, should I just suck it up and
switch over to carb; the smog will no longer be an issue, as I
might move oout of state. I just want my vw to be reliable again;
can you think of anything we might've missed?  HELLLLLP!

Answer
Hi Val,

This sounds like an easy fix (believe it or not).   The air flow meter (looks like a waffle iron on the top) -- has a plastic black cover on the bottom.

Under this cover is a large spring-loaded gear which controls the flow of air on the potentiometer. (activates the air vane)

Loosening this gear (i.e. making the vane less tight will restore the power, and stop the backfiring).   Mark the gear in it's current position, so when you go back for smog testing, you know where to put it back,  so it passes.

(also, change the points...the backfiring you described pits them immediately).

Let me know how you make out.

Don't worry, it will be fine!

Ron