It's possible there's a recall that needs to be done on your vehicle that
relates to the issue you're having.  Call your local Hyundai dealer with
your VIN and ask them to check for open recalls.  If recall 039 is open,
take the car in for the recall to be done.

Dealers in Northern Virginia are Alexandria, Brown's (Manassas), Fairfax,
and I believe another in Woodbridge whose name I cannot recall.  The
closest dealers across the bridge are Fitzgerald (Rockville) and Pohanka
(Marlow Heights).

If the recall has already been done, register for a free account at
www.hmaservice.com and check campaign bulletin 00-01-005.  To the best of
your ability verify the campaign has been done properly.

If the campaign has been done properly, you probably need a new air flow
sensor.  If you want to try this, it's simple enough to install.  Just
make sure the arrow indicating air flow direction points toward the
throttle body.  

The fact that the lamp went off means that there were three consecutive
drive cycles when the issue wasn't present.  As far as the computer is
concerned, it's fixed for now.

I don't know of any places other than dealers that are good with
driveability issues like yours.  That doesn't mean they don't exist, just
that I don't know about them.