Hesitation under load and no CEL, could be a sign of gas starvation. It could be just a clogged fuel filter or a fuel pump going bad. But in order to diagnose a fuel pump, you need special equipment to measure fuel pressures.
Also O2 sensors have been known to produce hesitation under acceleration when they start to fail, although not triggering a CEL.
Last edited by X3-terrestrial; 11-25-2012 at 08:55 AM.