Change INtake & head gasket, Now car lost power

[Tbx]

Gran prix 94 3.1L . I recently brought my car to the mechanic because the thermostat problem; at the same time I decide change the intake & head gasket because coolant was mixed with oil; the entire job was done. The car start working fine but after I speed 60Kph it lost power, the RPM gauge was so high 3500, now when you start the car RPM gauge is high speedometer is high too. Any clue what is wrong

[kilroypr]

There is an air leak somehere. Ask the guy that did the job to check al hoses and that he did in fact replaced the intake manifold gaskets as well. When taking the intake plenum appart of the engine always you should replace the gasket.