Most guys, if they are going to drill holes and install the threaded O2 inserts into the stock head pipes, will weld in 18mm bungs so wide band O2 sensors will fit in and can be used with a Power Commander 5 or 6 Controller using auto or target tune modules for tuning, auto tune for older bikes and Target tune for newer bikes that came stock with narrow band sensors. Stock narrow band sensors are slimmer at 12mm I believe it is and a bushing can be used to install the NB sensors in the 18MM bung if you so choose to run them - gives you the option. The db reducer is the quiet baffle available for the Bassani exhaust to quiet it down - also have you pulled out and checked muffler packing in the Bassani exhaust ? Stainless steel muffler packing is available if your fiberglass packing is blown out -
