ok first time i have posted something, but i need some help. My check engine light is on and i took it to the dealership to see whats up and they said i have a missfire code for all 4 cylinders and bank 1 is lean. I replaced all my plugs and put some injector cleaner and nothing. I replaced my MAF and ran a little better but still check engine light on. Also once i get above 4000 rpm my car starts to shutter and it also did it in low rpm before i replaced my MAF. I am lost on this i would appreciate any help i could get. I have a 2002 wrx 2.0l turbo so any tips or hints on whats going on would be appreciated.