I have a 93 Toyota Camry with 6 cylinders.  I have recently been
getting poor gas mileage and have been trying to figure out why.  I
have checked out the plug wires, plugs, and compression.  My
compression is great; all cylinders read between 170 and 175 pounds.
All plugs are a nice brown grey in color where it fires except #1.
This plug seemed carbon fouled.   I can't figure out why.

I put a tach on the engine and the idle wavers between 698 and 710
rpms.  I would like some ideas on why the idle would be drifting like
that.  My plug wires are relatively new; they only have about 10,000
miles on them and they are OEM from Toyota.   I checked the plug wires
to see if there was any voltage leakage.  I couldn't find any.  Also,
I put a vacuum gauge on the engine and found a vacuum of about 19# at
idle.  There was also a little drift of the vacuum (about 1-2#).  I'd
like some ideas on what to do next.