It reads at 9in.hg when at idle. Is this normal? I am trying to find out why my car wont idle at a constant RPM. When its cold it will idle at 2K and drop slowly. When its warm it will idle smooth and then chug for awile then go smooth again, and so on and so on. Anyone have any ideas? I resently replaced my fuel filter because it was bad, and my upstream o2 as well.