noise and fuel mileage are the benefits along with a longer lasting filter. drawback is a slight loss in power. you could go an entire season w/ one or two filters in an ins box.

try running the box back to back without the box. you will find you need to lean the engine 1/4- 1/2 with the box on with a barely noticeable loss in power.... hence the better fuel mileage.

i would run the box even if it was not mandatory. it gets you tuned in for when it is required. these days engines and pipes are made to recognize the fact ins boxes are required. 9886 pipe.... gone- it was made for no ins box and wide open racing w/ no ins box. three chamber pipes are "in" because they work well w/ ins boxes- thats what they were produced for.