3800 series 2 question?

I have a 99 Bonneville that has started to have a rough idle at stops where it will sit just right and then putter low for a second on and off the whole time I'm at stop lights. I changed the fuel filter and changed the wires and plugs a few months ago, and put in a new air filter as well. I can't hear any vacuum leaks, and no check engine light so probably not mass airflow sensor. Any thoughts? I may get a new pcv valve tomorrow and see what that does but I remember changing it not so long ago.