I just bought a 96 which hesitates at 60 to 70 MPH. I have changed the plugs and wires and the vehicle speed sensor. It also doesn't seem to have the power or acceleration of my 95 3.9L. Could this be the transmission slipping(checked fluid & it was over filled) or a vacuum leak?

 

Might check to see if your fuel pump is working right might have it pressure tested,I have a 96 and had new one put in