theres a very very good article out there on how to custom-machine you're own ITB's. it gives calculations for power based on the length of the runners, diameter, taper...all that. i'll see if i can link you....

EDIT: mk theres two. the first one is the general idea on how to make a set of ITB's out of some stock TBs (DSM?) and a skunk2 manifold...with some custom welding. the second one is for basic info and calculations on how to get a certain amount of power and at what RPM.

http://www.homemadeturbo.com/tech_projects/itb/

http://www.team-integra.net/sections...?ArticleID=484