For those of us that have to live with an annual state "emissions check" on our cars, do modifications such as CAI, throttle body size, etc. alter the emissions results and is there a chance that a car that is modified with such things could flunk the emissions test?

 

It really depends on what they check and what the state requirements are. A visual inspection of the EC devices would be the most significant issue. However, even if you've moded the car, for example put on a needswings DCAI, it may still pass visual inspection as long as all your required emissions control devices (factory) are still installed. Removal of a catalytic converter may / could result in failing the visual tampering inspection. If the state test is ONLY emissions (tailpite testing and code testing) then as long as it meets the emissions standards at idle (or on a dyno in some states) you could still receive your certificate.

Our state inspection is OBDII now so it's basically a plug and play test. They plug in the computer into the car's portal and it will determine if their are any emissions codes. If not, and your cat is visible, you're good to go for 2 years.

I had my car tuned (Eurochargeded) and the car passed fine. Then again, I haven't removed any EC devices or done any other add ons either, but it wouldn't matter because the only visual check they do is of the cat.

So, long story, it depends on what state you are in and what their inspection requirements are.