that plate seems kinda thin for a blocker plate, but it could be, hard to say what it is without seeing it removed. based on the second picture, id say it might be, though i dont see anything in the second picture that distinctly says deleted. The rubber cap is a resonator delete, which does nothing but remove some clutter, and it looks like a PCV rerout maybe, but again, both of those can be done with, or without an EGR delete. Looking at pictures of other LLY EGR coolers, they dont seem to have that tab, and im not able to find any pictures of factory seals that look like that, so if i had to guess id say its a very low quality EGR blocker plate, based on the wiring mess on top of the engine, im guessing that a lot of care and forethought was not previously put into that truck.
2015 Chevy Silverado 2500 HD 6.6L LML