GGB Mountain mufflers are designed to be used in areas where increased sound levels are not an issue. These cans are loud when you open the throttle. Please use accordingly and check your local laws for restrictions on modified exhaust. Sound level increase over stock (dbA) Idle + 4-6 / Under load + 10-18. Fuel and clutching mods are not necessary prior to installation. GGB two stroke mufflers are flow bench developed for back pressure against the stock muffler and will perform efficiently in any application where the stock muffler would be used. Both Mountain and Trail models are guaranteed to provide performance levels as good as or better than stock.