as previously said a noisy end can makes a big difference, i recently got an aftermarket can for my bike, and it's prettty loud, with it being a twin, its a proper burbly deep sound.... when i filter i constantly blip the throttle and make a racket,with the exhaust popping and fizzing people look in the mirrors to look for you wondering what the noise is. I think its made filtering a lot safer for me... personally i think filterings one of the most satisfying parts of motorbiking, just about doing it safely.