BOV BigBubba PlumBack Valve - SleeperBig Bubba From Turbosmart exists because sometimes Bigger is Better! It is a piston style valve for large capacity supercharged and turbocharged engines, including diesel. If you're looking for an inconspicuous valve for a small capacity, low boost daily driver, you must look elsewhere! Turbosmart's Boost Balance System means the more boost you feed this valve, the better it closes and sealsit is literally as simple as that. The 2 inch piston design