Staff member
I believe a 2004 Bonneville will be a carbureted model. Thruxtons were first introduced in 2004 and were carbureted as well. However, they switched to fuel-injection in 2008, which required oxygen sensors in the headers. Your best luck will be in using headers and silencers from the 2004-2008 Thruxtons. If you want to upgrade performance on your 2004, you might consider going with British Customs slip-on silencers that look original but do add performance: https://britishcustoms.com/collections/bonneville-carb?page=1&rb_product_type=Slip+On+Exhausts or the Norman Hyde slip-ons: https://normanhyde.co.uk/hinckley-triumph/bonneville-t100.html?hinckely_categories=3