My car has the 3.1 6 cylinder. It's worse when it's cold, but after I drive it for a while it seems to get better. I have replaced the fuel filter, air filter, spark plugs, and wires. The car idles like it is going to die, then revs back up for a second or so, then idles back down again, and repeats. I have done some research, and I think my next course of action will be to replace either the PCV Valve, or the EGR Valve.
But I'm not sure which one I should try. I have tried to test the PCV Valve by putting a piece of paper over the oil fill hole, and it never sucked the paper to the hole like I was expecting. But when I shake the PCV Valve, It rattles, so i'm not sure if it is clogged. I also hear what sounds like maybe a vacuum leak in the area of the PCV Valve, and I tried moving the valve, and the rubber grommet may be leaking air, as just the slightest touch creates a loud suction sound. So, PCV, or EGR, or something else?
I don't think it it those that you have mentioned. The engine is surging at cold start and this is a fault with the cold start and idling system. You should be looking at cleaning the throttle body and IAC.
For testing the PCV, you need to put it over the valve port itself and not the fill hole. Yes, the PCV seal is bad resulting in vacuum leaks.