abut the same, not higher than what would already be peak EGT, as the gasses exit, they are already consuming the oxygen required to burn all the fuel, as it exits into a higher oxygen atmosphere, then any remaining unburnt fuel would be burnt(if it running rich), temps being no different if all the oxygen and fuel combined inside a sealed cylinder at peak EGT, if it was running leaner, then there would be no excess fuel to burn, and the exhaust would already be oxygen rich,so the exiting gases would be entering into an area of yet more oxygen, but with no extra fuel to combine with it, the temps would cool, as well as expansion cooling of the gases exiting into a lower pressure area.