What I HAVE seen that causes your problem is that if you have an old, weakened oil saturated intercooler hose, the hose colapses when cold on accel. If that's happening, you can see it by watching the hoses when opening the throttle.
The solution to that is to simply replace the bad hose IF your dealer has one in stock (might need to be ordered).
An intercooler hose might also have a hole in it too but if so, acceleration would still be bad when warmed up too.
The hoses on all turbo cars eventually weaken, deteriorate with age because what IS inside those hoses is a slight oil mist, normal on ALL turbo cars and that oil eventually disolves the rubber hoses from the inside.
If any intercooler hoses look oily and/or are weak and spongy feeling, they should be replaced.