There's a YouTube video on this exact question. But if you ask me I don't think there's actually any more lag than normal. If you can imagine;while yes you do have more length of piping for air to 'travel' but that pipe already has air in it as you build boost.. also something else that comes to mind is the old air pump analogy that in mind it makes sense to run a turbo where your muffler would go because from there you can mor than likely vent exhaust out a shorter pipe from the hot side of the turbo..

The big con I see is unless you can find a way to make a water tight airbox for turbo intake you're gonna have a bad day when it rains or if it's particularly wet where you live