Well, first of all WOW you can type very well.
I would say your ventilation issues are a separate and unrelated. These cars the ventilation dampener and flaps seem to go all Mel Gibson on us.

The only code you have gotten is an EGR code?
My best guess is the catalytic converter, they go bad (get clogged) and rarely throw a code.
My other guess would be a stretched/worn timing belt.

A code checker is your best friend. Check early and check often. Just like voting.