Pennyman, On my e36 M3, many experts say the egr fills vacuum at part throttle in the BMW set up, supposedly helping mileage by reducing the resistance of piston movement due to increased vacuum in cylinders at part throttle. (admittedly this is a probably very small amount of drag, but on diesel trucks with egr, removing it adds about 4 mpg or 20% mpg improvement (and tq)! On these engines does it do the same thing, or just is there for emissions, choking performance with heated, oxygen depleted air? I haven't had time to study the systems working(s) yet..ANd may be going turbo diesel soon. Working on some Pajero 4D56's at a good price for us...