Hesitancy on throttle opening F355

Can someone tell me if it's normal behaviour with 355's (2.7 motronic) that when coming off the throttle quickly and then gently applying throttle again there is a very slight "hesitancy" before the engine catches as if there is a milisecond delay until the fuel is "squirted" again..........my car has this annoying effect and even after a complete renovation of the 4 throttle chambers done off the engine and the butterflies balanced with a manometer I still feel this hesitancy................2 qualified Ferrari mechanics have told me that this is a normal fact of the 355 engine....I find this hard to believe............all other cars are just smooth with the gas............by the way.........once this initial hesitancy has passed the throttle is absolutely smooth and progressive.....like a sewing machine in fact...............it's just that first milisecond from closing the throttles to then opening them again..........any thoughts????

 

have sorted my vacuum and butterflies.........I believe something else is at play here.........but what?

 

not normal "sticky throttle" problem