I'd be suspicious of a short-to-ground in the oxygen sensor.  When (if)
it acts up again, try disconnecting the single wire going to the O2
sensor on the left side of the engine (you can disconnect the 2 white wires
as well -- these run the heater in the sensor).  If it runs better, then
this will isolate the problem to the sensor (or more likely to the wiring
to the sensor).  Shorting this (black) wire to ground will make the FI
think that the engine is running very lean, and it will try to compensate
(same thing with a hole in your exhaust pipe, BTW).  you also should check the
voltage at this connection (with the wires connected).  Running normally,
this should vary from 0 to 1 volt.  If it sits at .45 or so, the sensor itself 
is probably also bad (it shouldn't sit still).  If it sit's on zero volts, then
you probably are grounded somewhere in this circuit.  The engine should run
pretty well with the wire disconnected -- there's a fallback mode in the FI
to account for a "bad" sensor, but your gas mileage will be terrible.

Also check farther down the mail for somebody else with a syncro problem
today.  These things had some wiring problems, and there's a reference to
a service bulletin that may also be of note to you.

good luck,

malcolm