Ok, sorry to belabor this one, and to the person who said it isn't really a
moral question, you're right. It's a question of strategy. Going forward,
here's a case in point.

The stumbling idle on my '84 1.9 is driving me nuts. No matter what I've
tried, with and without the help of the goodly folks here on the list,
nothing has helped. New O2 sensor with good ground, tested good on car.
Compression 155-155-145-130. No oil burning, no coolant leaks, no smoke,
plugs all textbook-beige. New dist. cap and rotor, new fuel pressure
regulator, new fuel filter, new idle switch tested good, rebuilt AFM, AAR
removed/cleaned/tested good in freezer and warm stove (car starts fine.) No
vacuum leaks--vacuum tests around 13 inches, and I've pulled the vacuum
lines time and again to check--all of them, even the ones at the AAR.
Removed, cleaned throttle body, sealed at inlet, no light shines through
butterfly valve. Changed oil, used Marvel Mystery in hopes that would help
lifters if they were air locked. Used Seafoam to get carbon out of cylinder
heads. Changed bad thermostat. Checked all grounds and built ground "web" to
all points in engine. Checked battery voltage at startup and running (over
12.5). New cat, new muffler, new rear engine mounts.

This may not be the definitive list, and yes, I'm guilty of throwing parts
at the problem rather than methodically testing the systems. But I'm
reaching the limits of my mechanical ability, never so great to begin with,
 as well as my sanity, and so am thinking of getting my mechanic to deal
with it.

Therein lies the rub.  He's a nice guy, easy to get along with, and has
always done good work, in the sense of replacing parts when they obviously
needed replacing. But what about the (dreaded) diagnostic question?

It's hard to tell him, OK, you have two hours to figure it out--then stop.
I've done all the obvious dumb stuff already. And it could be so many
different, unrelated things. Bad valve guides, as Dennis pointed out. Bad
Hall Sensor. Bad resistence on spark plug wires. Failing coil. Something
wrong in the distributor advance. Something in the vacuum system. Something
in the fuel delivery or injection system. This could take days to figure
out. And even then, it's an educated guess, esp. with internal engine
components.

So--instead of dealing with the problem in the past, as with the Boston Bob
business, Benny, etc., how to proceed going into one of these situations?

I'm almost thinking I'd rather leave it as is than deal with the mechanic
who can't figure it out and charges a few hundred of my precious dolares.

Sure wish some of the people on the list lived around the corner...

Sorry so long.

Geza