our track unfortunately has some stones lifting off the seal on the return road & after seeing 1 racer get a stone flick up from their front wheel & lodge itself into carbs butterflies, i would never ever run without some kind of filtration on my carb. the car with the stone in the butterflies took off with front brakes locked on & plowed into another racecar before the owner could shut it off. not a happy day for 2 racers that day. i'm using Frams Airhogg air cleaner. it's pretty good, virtualy no difference with it on or off, but i now leave it on.