Power loss in 2000 Montana

When I stop and start to go again I experience power loss. The Montana has no get up and go. It goes up from 2000-2500 RPM slowly. Then doesn't shift until over 3000. I took it to dealership and they could not find anything wrong when they hooked it up to the monitor. They cleaned a censor but could not give me a diagnoses. Has anyone else had this problem and had it solved?