misfire and running lean

hi i have a 2006 gti with 160k miles i bought the car last year and i was told it is apr stage 2 with the high pressure fuel pump im not sure if it really has a hp pump this is my first german car. ive been having really bad wastegate rattle so i changed the turbo with a oem turbo and ever since ive been having a misfire on all 4 cylinders with bank 1 lean code it runs really rough at idle but fine 1st gear though 3rd then over half throttle it breaks up sometimes in the rest of the gears i changed the plugs, and the coil packs are apr i
wanna know whats the next step see if theres a vac leak, injectors, hp pump, lp pump ect. i dont wanna load the parts cannon.