They told me it looked good. It is running a tad richer then when I had the larger spacer installed, but the plugs look good and it runs well, so they said not to bother going down a jet size. Running rich will result in a higher CO reading. Running lean will result in a higher O2 reading. All I know is what I read from this www.crypton.co.za/Tto%20know/Emissions/exhaust%20emissions.html