You need to get your chemical formula right. NOx is the smog forming emissions spewed out the tailpipe. N2O is nitrous oxide.

N2O is 36% oxygen by weight. When the nitrous oxide is heated to approximately 572*F it breaks down to release extra oxygen. The nitrogen that is part of N2O performs an important "buffering or dampening" of the increased cylinder pressures making combustion smoother and more controlled.