Okay - forget everything else...

Are Carbs really THAT much more thirsty than ITB's?

Sorry, what are ITB's?

Individual Throttle Bodies. SOmeone's been reading Honda-Tech too much

Yes, they fecking well are! 18mpg on a tuned Zetec on 45s is not funny!

Depends

A well set up carb can come quite close to the ideal fuelling for an engine over most of it's operating range, in which case the difference between carbs and injection/throttle bodies will be minimal. However carbs that get that well set up are few and far between. Many people don't even have the right size body and chokes let alone going as far as properly tuning the carb, most do the main jets and idle and leave it pretty much at that. By the same token a poorly mapped injection system will be just as bad.