Eaton M90's are only like $400 from a junkyard (they were OE on the 3800SC GM engines (GTP, Bonneville, Regal, etc)). That's why they're so attractive to use on custom jobs. What sucks about them is that they come with a really funky flange face that you have to make another end to in order to get the boost up to the throttle body or into the intake manifold.