I noticed that there is a plug of sorts that looks like it could be screwed in more. If you're looking at the engine bay, follow the intake up to where the EGR is. Just past that, right next to the plenum is a plug.
I'm not sure what this is but it screws in, and some of the threading is exposed and has some light rust on it, as if it was screwed in at one point, but has since come loose. Any ideas on what this is and whether or not this could be causing the SES light to go on? I have a not so hot picture, but I can't figure out how to post it so if you want to see it, PM me with your e-mail address and I'll get it to you.