My car used to chug also at idle bouncing between 600 and 800 rpm got it fixed by putting the small o-ring and spring that was missing on the PCV for some reason previous owner of the car took them out. and when I bought the car I didn't know it came with those missing parts and only swapped the PCV out for the new one. It was until a few days ago I asked here on the forum and they pointed me in the right direction. What I did notice on mine was that with the engine on I took the oil cap off and I could hear the engine sucking in air, check if yours does the same thing and also if the 2 o-rings (one small goes on the PVC and one large on the twist cap) and spring are there.
