Sorry....my computer has gone down several times.....BAD storms!
Sure, I have had similar problems. Deal with this nearly daily on all different makes and models. All I can tell you is that the engine is getting air from some place it is not supposed to be getting air from. I cannot tell you exactly where - because there are too many variables involved here....
What I can tell you is that the problem is not due to any air going through the throttle body as long as it is going through the mass airflow sensor first. This would pretty much eliminate any theory of the throttle plate angle thing causing the problem. The code you are getting (P2279) indicates that the computer has determined that the engine is getting air that is not going through the mass airflow sensor.
The other code (P0507) indicates that the air that the engine is getting is downstream from the idle air control - meaning that shutting the idle air control off fails to slow the engine down. So basically, you are looking for a vacuum leak that will allow air directly into the manifold without going through the mass airflow sensor or the idle air control.
A can of carb cleaner might be very helpful in locating the leak.
Also make sure that all the things that are SUPPOSED to have vacuum have it (Brake booster, purge control solenoid, HVAC controls, etc.).