I have a 98 venture. For some time now it will stumble or chug when I am going at hiway speed - it usually happens when I start to climb a hill but it hasen't shifted down yet. Once it downshifts it smoothes out and accelerates fine. It feels like it isn't getting enough gas.
I have had the intake manifold done, the ignition wires changed and the injectors flushed with little improvement. I have seen similar problems identified but have never seen a solution.