First thing I would look at is the Gizzmo boost controller mate... There terrible for holding boost IMO.. Ive had one on my Glanza and on an S14 and they were really poor. Are you running external wastegate?. If so, I would put a 0.9 bar spring in there and run the turbo directly off wastegate pressure and see if that changes anything. You could do the same if you are using an adjustable actuator, wind it out to 0.9 and run it off that. That's my first go to mate! Matt