The EGR (exhaust gas recirculation) put exhaust gases, via a valve, into the intake. The middle pic is the pipe plug in the intake, also in the middle of the frame. I took the whole thing off, and plugged the exhaust ant intake manifold holes.
If it happened WOT or close to it, it ain't the EGR unless it's sticking open. Sounds like an excellent excuse for an L67 top swap. 😎