I have power loss below 1,800rpm when the engine is cold. The power will cut out and come back randomly. It only happens when the engine is cold for the first few minutes of driving and there is also sometimes a sound like air dumping, but it's not the recirc' valve as the boost gauge doesn't move and I have tested it with the valve blocked off. Also had a vac leek test done and it was fine. Once warm this doesn't happen and the power is very smooth low down. No codes showing.