Engine knocking when cold

Recently had my car (CR170) remapped and all was fine for about 10 days or so. Then one morning the car struggled with power, hesitating at about 2000 rpm and felt like it was wobbling quite badly, some white smoke from the exhaust but that only happened once and the engine was making a loud knocking sound like there was no oil in there, this cleared up and went back to normal after 5 minutes of very careful driving. The cars been back to the guy that's remapped it and he picked up the same issue when cold. Haven't got a definite answer from him and he says it could be injectors or fuel filter. He's since removed the map and took it back to standard and the issue was still there this morning. Wondering if anyone's had the same or similar experience to shed some light on this?

I haven't checked it no, I don't have a boost gauge but after 5 minutes everything returns to normal and the turbo spools up fine. After doing a bit of reading yesterday and speaking to a few specialists it's been narrowed down to injectors, oil pump, glow plugs or the timing belt being a bit stretched although the guy didn't seem too convinced because it doesn't happen all the time. Would've thought 3/4 of these problems would've either shown up on VAGCOM OR VCDS or thrown a warning light up?