This link has some info on cleaning the throttle body and EGR passages. You may be getting a CEL from a blocked EGR passage. You can do some searching on CEG to see if you see any more. But you might have your mechanic
1: Clean the throttle body and the EGR passages behind the throttle (the 4th photo down, you see those blackend groves? Those are the passages. They get gunked up pretty bad with carbon & gunk.
2: Maybe a new EGR valve while you're at it. Might also have him check those vacuum lines going into the EGR valve as well.
3: The IMRC opens your secondaries.
This link gives a little info on that.
Good luck!
OH, and unplug your battery positive for 20 minutes when doing this to clear any stored fault codes in the computer.
