Does the check engine light come on? A lot of hesitation can be a number of things. The 02 sensors could do that, the egr valve, fast idle valve or timing can cause that problem. It also can be a dist. problem, the vacuum advance might not be working properly. What you need to do is work on one of these possible things one at a time. It is hard to just tell you what it is since I am not there to see or hear the car.