RE: 2000 3.0 misfire @ idle
I had the same problem. Thought it was going to be bad, $$$ but it ended up being a broken hose at the PVC valve. The hose is a formed part. it split at the elbow that attaches to the PVC.
I cut the hose and used a new PVC valve that had an elbow built onto it. That way the hose can stay straight. Cant remember the Part #.
If you hear an air sucking noise with the hood open, you may have the same problem.