7AT super slow shifts and throttle response

[T-Rex57]

Hey all, I've searched the forum but not sure the existing answers solve my particular problem

Slow shifts have always been a problem with my car, pre and post UPREV tune, but it seems to be getting worse.

About 9/10 times the car shifts very, very slowly in most conditions, in D or M with or without VDC on (though there seems to be a slight improvement with VDC off). It doesn't matter what the ambient temperature is, in traffic or highway conditions there seems to be a general utter lack of throttle response. Merging onto a highway from say 60km/h (37mph) to 100km/h (62 mph) with linear and controlled foot movement means a wait of a 2/3 seconds before the car accelerates, accompanied with an audible rise in revs

From a standstill - sometimes it will go on demand - but most of the time if I stomp on the gas pedal the car will think about it for up to 6 seconds (actually timed this) then dump power and take off. The power delivery isn't linear or predictable (despite what the dyno shows)

Things I've tried:

• Had the car checked by mechanics who could find nothing
• Checked by tuner
• There are no fault codes via ODBII
• Other intakes (Gruppe-M, STILLEN)
• VDC toggle
• D/M mode

The car is UPREV tuned with 220rwkw (300hp) at the wheels with an ARK Grip V2 exhaust, Fast Intentions HFC's and (currently) standard intakes.

Keen to hear any advice before I try weird ideas like throttle controllers and grounding kits