rs250gpracer

my uk turbo final classic car seems to hesitate then jerk during gearchanges when driving hard through the revs allmost as if there is nothin for less than a second then.. boom everything!!!
also when rolling off the throtle from high revs it seems to hesitate then decellerates, its quite a jump though and sometimes can upset the car a bit. i would of thought the initial transition from full boost full throttle to low throttle or even no throttle wouldnt be this bad, ive had the car well ove 12 months its allways been the same just starting to lead to far to many mid conrer upsets, even say on a duel carrige way and only slight bend coming off near full boost to no boost can upset the cardriven all other ways the car is fine, still drives like new, feels good, boosts well, it does seem that boost may play part of it seen as its when changing up gears from high rpm... or coming off the throttle from full boost.