It is probably about the point where replacing the plug wires could be beneficial, so consider that. Personally I'd buy stock wires again from QSubaru or Troncalli. I advocate changing plugs every 15,000 to 25,000 miles for optimum performance and fuel economy.
You also are way overdue for a fuel filter if that hasn't been changed at least once... that could certainly cause hesitation. Another possibility is bad gas-- too low octane, too much (in winter), oxygenated gas in general, water in the fuel...
And sadly, another likely possibility is the fragile MAF sensor.
[This message has been edited by ColinL (edited February 01, 2001).]