1.8,16v 2000 laguna engine runnin like a bag of .... ?

Some one please explain how the engine managment works on these cars,the car over revs and has not much power. Replaced the clutch (hideing a misfire,changed the lamber sensor(still the same)changed the 4 coil paks (german ones) and put in champion e-on plugs (still the same) replaced the timing belt(still the same)this car is drivin me abserlutly crackerzz,have just read on this site someone lookin for his air flow meter?,been told it could be my throttle possision sensor and if any one of these sensors go down (airflow/throttle) the whole ecu goes to pot, please help as sick of spending hard up cash on this french car... Paul on the wirral