[mwebb]

no
the AF mixture is not "rich" or "lean" when EGR is operating .
because these systems are feedback systems , the ECM responds to inputs from the AFR or 02 sensor to keep the mixture at stoich , 14.7 to 1

systems with AFR sensors can operate rich or lean of stoich BUT the ECM still will maintain Air Fuel ration where the ECM wants it to be using information from the AFR sensor , in these systems the ECM can maintain the Air Fuel ratio where it is programmed to with out changing due to
EGR operation .

so
Combustion pressure is reduced by the presence of the INert gases which do take up space but do not support combustion
the INert gases behave like a cushion , to reduce compression ratio and therefore combustion pressure
while EGR is operational

combustion temperature IS reduced because Combustion pressure IS reduced,
not the other way around

NOX forms at high temperatures Reducing combustion pressure also reduces Combustion temperature which
reduces NOX formation
EGR is Good .

EGR does NOT increase Power output
EGR does not reduce maximum power output because EGR does not operate at WOT or close to WOT
WOT = Wide Open Throttle
EGR on a gasoline engine does NOT operate at idle

EGR is good

KISS
thank me very much