You're going to have be a bit more specific. When, exactly, does it hesitate? Warm, cold or both? Off-idle or at higher loads? How severe is the hesitation (small hiccup or full-blown misfire?)
What mods are on the car? When did it start showing symptoms and did the onset correspond to any service/work you did or had done to the car? When I say "any" I mean any, from cleaning the car or engine bay to have long-tube headers installed...
Do you see a MIL (malfunction indicator lamp)/service engine soon light?
It happens more often on warm. But has happened wen cold also.
Usually when I'm at a stop light and gonna take off is when it hesitates really bad. at idle I do smell like raw gas from exhaust.
My car only has a k&n CAI. And flow masters cat back.