I don't mean to sound nasty Rezlo - but is there anyone else in your part of the world who is fully versed with webers? Gotta be honest, if he couldn't notice a big crack, and thinks flimsy linkages are 'ok' (hell that's practically the first thing ANYONE will say about multicarb setups - use sturdy consistent reliable linkages or don't even bother trying) - I have to wonder whether he deserves any reputation as a carb guru.

This 'should' have been checked - but are hte needle and seats definitely new?? if they have a ridge worn into them, you can 'trick' them into closing right with a lower float setting which pushes them harder by the time the fuel level is where it ought to be, but then when you expose them to odd conditions (like high g forces) they can sort of 'stick' on the ridge and not close properly, and start flooding the carb (on decel likely as not!) alternately they can have the 'right' float setting at idle, but then when fuel demand increases that 'too low' float static setting starts to actually limit the fuel coming into the fuel bowl just enough to lower it's level, leaning it out - usually at the end of a straight as you get near peak rpms in top gear, just before the braking area).

just random thoughts