NEED MORE INPUT! (as Johnny #5 said in Short Circuit)...
Did your PT NOT hesitate a bit before you installed the new exhaust? Most of the people that complained had a hesitation from the very start before any modifications. It's hard to believe that just changing the exhaust has brought about your hesitation, usually it's some sort of modification that's done to the engine that brings about rough/stumbling/hesitation (pick one). The problem has been covered quite extensively in this and other forums and the answers run from fixes on the computer (if your car has a build date before Aug 22, 2000, to disconnecting the negative battery terminal and then running your car the way you want the computer to learn how you drive. Hope that helps a bit. <img src=icon_smile_big.gif border=0 align=middle>
CREWZIN