BD Diesel Exhaust Brake Variable Vane - Chevy 2006-2007 LBZ DuramaxThe variable vane turbocharger design used in the 2004. 5 up Duramax engines to reduce turbo lag and increase power can also help slow you down. BD utilizes this technology to electronically close off the vanes which can create up to 130 retarding horsepower. This braking force will help to maintain your speeds on descents and curves, giving you better control of your truck and load. While in Tow Haul mode, switch BDs Variable Vane Brake (VVB) on and