95 Olds Cutlass Supreme bucking during acceleration

95 Oldsmobile Cutlass Supreme 3.1L Sedan, 135K miles. Car hesitates, bucks, and surges at about 30 mph when accelerating from a stop, especially with A/C on until you get up to cruising speed, and then it seems fine. Very annoying at stop lights/signs. It hesitates and surges unless you rev it and really give it the gas. Changed fuel filter, air filter, plugs, and wires - still surge and bucks. Went on a fairly long trip (2000 miles round trip), and my highway fuel economy has dropped from about 29mpg to about 25mpg.