This is a very exciting thread particularly to me. I have one set of Toyota individul throttle bodies in hand also planning to bolt on the D23 engine. They are 45mm each diameter with stock idle bypass and vacum slots for brake and etc. My point of using ITB is much less for hp, but much more for a trial (Just wanna do it). I heard ITB helps power all across the rpm range with the best throttle reaction. However it is also the most difficult to tune. Today it is somehow almost extinct on production cars, with the exception of BMW M cars. Even Farraris do not use it. I do not know why, but in fact single throttle can creat almost the same power as ITBs (but not as good torque curve). Maybe it is because it is just too messy to tune it periodically? FYI the FAQ column in
http://www.jenvey.co.uk/ is quite informative. I have not started my project yet, but once I do I will also post here.