2000 sebring convertible ohc wont kick in?....

I just had a water pump replaced and new spark plugs wires and timing belt installed the car runs and shifts fine ... except when I put the car to the test and try to speed off then once I hit 4000 rpms it bogs down big time but once i release the pedal it shifts and runs fine.... is it my over head cam not working?.... timing off?... I feel a slight vibration when I am idling at a stop sign