What is your exhaust temp?

[RRoyce4u@aol.com (RRoyce4u@aol.com)]

What is your exhaust temp and did it pass emissions?  
My 16v failed emissions and I was wondering if you could adjust air/fuel ratio by measuring the exhaust temp? My car failed on Nox only. NOx is created when your engine internal temp reaches 2500 degrees. I measured my exhaust temp after emissions and it was greater than 220 degrees. After I enriched the fuel by a 1/8 turn the temp dropped to 170 degrees. Am I on to something or way off base?