Hi Fred, thanks for initiating contact. An air injection fitting, in the context of exhaust systems, is a component that allows for the connection of an air injection system to the exhaust headers. This fitting is designed to introduce fresh air into the exhaust stream to help reduce emissions by promoting more complete combustion of fuel in the engine. In your case, with collectors on your headers and three bolts, it seems like you have a different setup than one requiring air injection fittings. Collectors are where the exhaust gases from different cylinders combine before exiting the exhaust system. The presence of three bolts indicates a different type of connection compared to air injection fittings, which are typically used for emissions control purposes. I suggest calling our parts specialists at 1-866-529-0412 to provide the vehicle information so we can help you look for the right part. Have a good one.