It looks like it’s wild theory time. For an explosion to occur, there has to be fuel and air containing oxygen. How could both fuel and oxygen get into the EGR valve? Vacuum acts on the EGR valve and the EGR pressure sensor. The vacuum source starts at the engine intake manifold, and gets distributed around the engine via lines and hoses. Because of varying restrictions in the lines/hoses, the vacuum won’t be the same in all.
What are the possible fuel sources? The fuel pressure regulator has a vacuum hose attached to it. If the fuel pressure regulator diaphragm were to leak, the fuel would go into the vacuum lines/hoses and on into the intake manifold; except, if it didn’t go directly. If a line/hose had less vacuum, say on one side of the EGR valve, or EGR pressure sensing valve, the fuel/air could get to the hot EGR valve, and KA-POWIE!
Same possible scenario with the charcoal canister purge —which is a vacuum hose, right?