citroen c5 2.0hpi sounds like a diesel?

53 plate citroen c5 2.0hpi top end knocking sounds like a diesel but when reved up gets a bit quiter but not alot have changed the lifters and the front cam sprocket for the vvt and have changed the camshaft position actuator now change unless i power the actuator up with a power probe then is lovely for 2 mins and starts to get loud again have checked wires nothing there have checked old and new actuators both fine.