I know a wideband will let you know if your car is running rich or lean. But what all do people use them for diagnosing or tuning. And how? I am trying to learn everything I can Right now. I am wanting my build my fd. The most I have done mechanicly with my fd is removed the motor to paint the car. So if you guys know of anygood sites that Give a lot of information also. please let me know thanks.