A scan tool would be helpful to look at engine data. Ensure the engine is in closed loop fuel control,O2 sensor is functioning properly,fuel trim data is in range,coolant temp is correct,etc. NOx is created by combustion chamber heat.....anything that could cause combustion chamber temps to go up will increase NOx production. EGR is designed to reduce those temps...just because it's new doesn't mean it's working correctly. Lastly the reduction portion of the 3-way cat is designed to reduce NOx at the tailpipe.