Will adding headers increase my engines emissions?

Will adding headers to my 1991 240sx increase the emissions? or decrease them due to the increase in efficiency?

More exhaust flow = more emissions.

If the car runs well though it won’t make you not pass an e-test.

i was thinking it would do that , but would it not make the car run cleaner because it would be more completely cleaning out the combustion chamber?

Would it lower Combustion chamber temperatures. therefore lowering nox?