Check the small and large breather hoses plus the IACV. I had the same problem with mine recently (also 2.0l 16v), was going to do it all as per the guide this weekend but forgot to pick up new gaskets for the IACV and throttle body. Use the link H21 provided for info, thats exactly what I followed.
However, I did take of the small and large breather hoses, small one was quite clogged up with gunk and the large had a fairly good load in it as well. I just cleaned them out with carb cleaner, then washed them out and let them dry. To clean, I just bent the pipe in half (so it was U shaped) then effectively filled them up slowly with carb cleaner and let it do its magic.
Also, if you take the small pipe off, check the bit it attaches to on the cam cover. That hole will probably be a bit clogged up also. I used a small screw to clean mine, just gently screwed it into the caked on muck, then pulled it out, this brings all the muck out attached to the screw thread. Make sure the screw is smaller than the hole so you are not actually threading into the sides of the pipe on the cam cover.
It is idling a bit better now. If it is this, you probably won't get any fault codes, or at least I didn't.
Note: If you are going to do it, and it isn't that big a job in my opinion (I am not a mechanic

) make sure you get the IACV and/or throttle body gaskets. The small hose is a right bitch to get off and back on with them in place.