if you find any solutions, do let us know.
its the same problem with my car. boost buildup is fine. after around 3500rpm, it feels "empty". then between 6000-7000rpm, it feels ok(can feel the g force). no boostcut on my car, no airfilter installed (not running airflow), VCT running ok. car is bone stock except for walbro 255, megasquirt EMS. its not about tuning. feels like no boost. boost leak check OK.