Hi

I have this Ford Focus in, when it warms up customer says it starts to misfire or loss power under 2000rmp before turbo kicks in 25 to 35 mph I have had it for a day can't make it happen. I changed a leaking air pipe & air flow metre but customer says no change live data looks ok but dnt have data of when fault present. It only has 1 code in memory 138b i think thats something todo with glow plugs?

Any help will be great

Joe