Important: Mazda B2200 and B2000 trucks have an EGR system. The EGR connects to the air cleaner. If a back pressure valve (reed valve) or component in this EGR system goes bad it will send exhaust gas into the carburetor. It was not designed to do this. The symptoms are exhaust type (oily) soot inside your air cleaner. This is evidence that a problem exists with the EGR system. This problem usually causes carburetor failure but also needs to be fixed for your newly purchased carburetor to work properly.