The next easy/cheap thing to do is replace the PCV. Ours are notorious for clogging. It doesn't seem like it would be the cause but it is listed as one of the possibilities.

Another thing to try is to add a bottle of fuel treatment to the tank. Another cheap/easy thing to try but I wouldn't hold out much hope of it making a significant difference.

The last easy thing to try (if you can find it in your area) is to fill up with a full tank of ethanol free fuel. When my Proton's MAF was acting wonky, it only threw a code whenever I was below 1/2 tank.