To begin with, state year, model, engine, transmission of your car. Describe in more detail your hesitation problem. Before thinking about installing a high performance chip or complete ECU, fix your hesitation problem first.
^^agreed^^ A programmer is not going to fix a hesitation problem, so clear that up first. As far as programmers, UPREV is considered to be one of the best, especially if you have made any performance mods to the vehicle. They'll create custom tunes for you ECM. For more info: