My car is running on four cylinders. However, it doesn't have much power when accelerating in First gear.
A six cylinder engine running on only four cylinders would be a low power situation. The two cylinders that are not working would need to be checked, to see if the injectors are working. These vehicles have a history of problems with the injectors, injector harnesses, coils, and oil leaking from the valve covers. I suggest contacting a mechanic, such as one from YourMechanic, to diagnose your loss of power issue, to see why the engine is only running on four cylinders.