boost bottle

I see these things for sale but don't get the function. What exactly do these things do and how do they work. Is it worth it to put one on for some extra umph up the hills. I live in Pa and everywhere but in the valley your either going uphill or downhill. Possibly I should go right to the nitrous. I would probably need the quart bottle of nitrous though.

Back when I used to race motorcycles I put an expansion chamber on my bike. The excessive noise would surely attract the police. It works really well but the noise level would be unexceptable around the neighborhood. Now if they made one that was quiet, I might consider it.