Here in Ga. the emissons test will plug directly to your car and read all the data stored in the ecm.Any mods made that affect the stock settings can be detected.This data can cause the car to fail the test and cost you a lot time and money trying to get it to pass.Be sure to check with the person doing the mod to make sure it will work.I bought a lot of SLP parts for my Trans Am that I had problems with.Try bigger diameter pipes and a bigger converter.That works for me on all my vehicles.