Right...
First things first...
Take OFF the FPR. Make sure you don't have a FCD wired in on it tho...
If you hitting fuel cut at 0.85bar its all good..
The LAG, is most likely because the adjustable wastegate actuator is not tensioned properly...
As a starting point, It wants to be JUST tensioning the flap with no vacuum interference...
Hitting Fuel cut will most likely be this cold weather and the combo of a front mounted filter and huge decat...