Performance Chips and emissions?

[scottewid]

Does anyone know if performance chips will affect emissions? My 86 951 has Weltmeisters and it just barely passed the NJ 15mph dyno test. HCs and CO were well under limits, but NOx was just a hair under the max. My 84 na passed all the tests so far under the limits, that the inspection guys were amazed at how clean running it was. Just curious if it's the chips, or maybe I need a new O2 sensor? Car runs fine and gets very good mileage, which makes me doubt its the O2 sensor.