My thanks to all who sent advice on my problems with
my engine repeatedly losing speed and then surging after
a few hours of highway driving.  I thought I'd summarize
the suggestions I got, for the benefit of others who might
run into the same problem.

Roughly in descending order of popularity:

(1) The air flow meter harness "capacitor fix" - a 22 mfd 35 volt
    capacitor between pins 2 (+) and 4 (-) on the AFM harness, to
    smooth out electrical jumps that confuse the computer when
    vibration causes the AFM wiper arm to lose contact.  If needed,
    adjust wiper arm a bit to make better contact.
(2) Replace the fuel filter.
(3) Replace the O2 sensor (particularly since it's time to replace it
    in any case).
(4) Replace coolant temperature sensor.
(5) Check for weak battery.
(6) Check engine electrical connections for loose wires, etc (always
    a good idea).

It's time for a new O2 sensor anyway, and probably time for a new
fuel filter.  The capacitor fix is inexpensive (about 79 cents) and
easy, and harmless even if it's not the problem.  So, I'll go ahead
and do everything but the coolant sensor (since that's $20-30).
If the problem doesn't go away, I'll try the coolant sensor too.

Now to go get my Bentley and find out where the AFM is...
(yes, I'm engine-illiterate).  (But I *do* know where my fuel
filter is.  I found it one day when the gas line came
disconnected from it while I was driving down the highway,
and I lost the whole tank in about 15 minutes.)

                                             -Steven Sittser