google is your friend!! I just put in "how to pass an emissions test" and got back thousands of results. You will have to go trought them to see what is BS and what is legit.
http://www.squidoo.com/howtopassemissionstest
Also, filling up your fuel tank with gasoline that contains 10% ethanol alcohol (many premium grade fuels use alcohol as an octane booster) may help lower your emissions even more. Many areas now have "reformulated" gasoline that contains alcohol or MBTE that adds oxygen to the fuel to reduce carbon monoxide and hydrocarbon emissions.
The Fuel Atomizer 2000 has helped people pass the emission test all along the west coast. I work for Wyoming Kustom GEAR LLC. so I might come across being partial but, people have reported tremendous results. A car up in Canada was reading 1620ppm of hydro-carbons and it brought it down to zero. It cost about $150 but it also cleans the inside of the engine and increases mileage. Let me know if you want more info.
http://www.heartland.org/publications/environment%20climate/article/13139/How_to_Pass_Your_Emissions_Test.html