Total aside @ALB -- but have you seen Johannes Persson's (JPM) IDA kit? It adds a "tri-jet" stack similar to the Dellortos. He calls is the Raptor Power Jet kit. The idea is that the additional jet acts as a main-jet, with the IDA mains dropping a few sizes to become midrange jets, with the idles staying the same.
He's also got a trick grooved venturi setup that will increase the flow on a set of 42 mm vents by 19 cfm. This is enough of a flow increase that almost nobody would need to go to the 51 mm modification (although he's got the grooved vents for those as well).
It's super-trick stuff for the guys way, way out on the edge (big turbos, etc.) who don't want to go EFI.
