Polo 1.9TDI 2002/3..ATD engine...i adjusted the idle on the car,it seemed a lot quieter on idle than before,ive put it back to standard as i wasnt too sure if i would cause any issues. What i want to know is....is it worth doing,any benefits ? or is it best left at the factory setting,it currently shows on vcds to be idleing at 903 rpm, (this normal)it is a tad high than what vcds states in the range which i cant remember but i think its 870 or 890 rpm at the highest. car was at normal temp and no faults were logged. 58K full vw history.