I'm after a small portable compressor that allows you to set the pressure you want it to maintain (down to 2psi for finding vacuum leaks in emissions systems), and which will work silently (when it's not refilling the tank). What's the entry level price for something like that? I've been using a digital tyre inflator up till now, the main problem being that there's no tank, so it's always making a loud noise while it's running.