Re: Replaced the pcv valve with a filter...
In the "old" days, motors did not have a PVC valve, just a filter in the valve cover similar to what you have done. The gases from the block were vented through an opening in the side of the oil pan. This was a bad thing for mother earth as all that oil that now ends up in your air filter from blow by would just fall on the ground and the gases from hot oil and combustion would end up in the air adding to the smog problem.
I would think that your idle problem stems from a vacuum problem as you have altered how much (or how easy) air now gets into the intake manifold. (The PVC valve restricts the air flow.)