[Lord of Hog]

I fitted a K&N panel filter and replaced the restrictive venturi at the end of the Shannon tube with a medium mesh cover. That made a small but noticeable difference. Of course if you increase the intake flow then you'll really only get the benefit if you similarly increase the exhaust flow. A nice Stainless Steel cat back done by a decent outfit who can remove existing silencer boxes and replace them with custom jobs is the way forward. The Rover system is pretty much free of bends and tangles, apart from that daft bend where the rear box joins on. It's a question of balancing what you're prepared to take in increased noise against performance.