bad idling

hello. im having an e46 318i 2000 model. it starts just perfectly.the problem is that ; the idling is bad, as it idles i can see the rev count moving up and down around 500 and 1000. i bought a new starter,a new coil, a new set of HT cable.i bought a new pick up sensor.
as i try to press the accelerator,the revs take too long to pick up....so please.