engine pinging

[jwest]

Considering all of this, isn't it feasible that if the EGR isn't functioning correctly, you'd get the pinging also? Or would a bad EGR be apparent in other symptoms? (considering that the EGR is there to bring down combustion chamber temp)

Just speculating here...

Not only is it feasible, it's probable.
IMO, a no EGR condition in a system for which it was designed, like ours, would directly cause the detonation scenario to be compounded.

As you pointed out, EGR is introduced into the combustion process as inert gas, essentially decreasing displacement and reducing combustion chamber temps. In our system, timing is advanced and balanced in compensation and anticipation of EGR.

Now, a mechanical distributor vacuum advance like ours, doesn't know when EGR is present or not.
So without EGR, not only are you running hotter, but you're also running advanced.