so i just changed out the original turbo on my 03 wrx and about a month ago put a walbro 255 fuel pump. i got a turbo which is the same as stock (tdo4)from a guy who parted out his car and it has aprox 30k miles on it. and after swaping the turbo my friend checked everything out with his snap on comp and it showed me running a little lean. so he loosened the wastegate to turn the boost down and now im maxing out at 10 lbs of boost and it was running fine. but after shutting it off to get food when i get back and turn it on it sounds like it has a big cam just idling rough maybe about 200 rpm. and there is black smoke comming from the exhaust. any ideas on what it can be?
cobb ap stg2
any help would be great