is it a adjustable actuator? i dont know your set up, but if uve decatted you may be getting huge boost creep so by setting the actuator to where you want the boost (12psi im guessing) then its actually too slack on the wastegate flap, so its letting exhaust gases through prematurely, resulting in late spool up. thats a wild guess because like i said i dont know your setup. if thats your problem then only thing you can do is try and get rid of the boost creep by putting a restriction some where (intake or exhaust), also porting the wastegate may help. or do what i did and buy a aftermarket ecu and up boost which in turn will put more pressure on the wastegate flap when its closed. Carl