Yep, like I said, Open loop (WOT) closes EGR. At other times the engine runs closed loop and corrects itself. These corrections are learnt and used for future engine operation.

The guy is presumably driving a DF so it's going to be running on the fat side of 14.7:1 anyway, and these early 5.0's respond well to a timing bump. Sounds like some good reasons to block the EGR flow....

And FWIW I don't get a hint of detonation in my EGR eliminated 5.0 with base timing at 34 and running regular 91 octane fuel. I rebuilt the engine about 50,000k's ago (with flat top pistons, rather than dished) so it's still nice and fresh, and not a compression compromised engine.

You're missing the point read my post again.