IMHO the DD version is a rip off. The cheapest way to go is to just simply add a jet in the line, but you have to be a bit more careful as it is not adjustable. As for the BMP kit it is definitely a top notch piece, adjustable and CHEAPER then DD. Both will come with quality liquid filled gauges I believe the DD's gauge is smaller in Diamater but other then that no real difference. Also, SpeedWerx1000 (an HCS member) may have a few still lying around as he used to make them...again cheaper then both the above and exactly the same as BMPs.
Mike