[new xc90 guy]

Hi group. After some help please literally Brought my 2008 2.0d v50 3 weeks ago 2 out of the 3 its been sat on my drive in bits. The seller started it before I arrived to clear the smoke.
anyway I brought it! I did notice after driving it on the the motorway for an hour and half it had a very faint misfire/idle lumpy. Which I absolutely hate.
next morning i started it and the smoke was embarrassing its was a whitey blue and It lasted for about 1-2 mins engine was juddering and clapping like a tractor very roughly then after a few minutes smoke clears and engines fine . And drives fine however still with a offish idle.
so i took it up on myself to remove the injectors to see leaks with scope' camera.. didn't fit in hole then took off the egr to remove glow plugs found 3 and 4 wet. Whilst i was there I removed the turbo as well as that sounded funny on these. Anyway. Brought some new glow plugs and a set of injectors second hand ones apparently tested. After days of graft put it back together to have it slightly worse! And no I didn't code injectors as a guy said if the number on top is the same its fine. Mine were 5s being replaced with 5s.. anyhow ran worse I believe. So I've put back my original injectors after leaving them in brake cleaner all day and it ran alot smoother still smoked and had that rough idle. Now this car hasn't had a service in over a year surly a fuel filter wouldn't cause this. Here's the mad issue I need to understand. I did a leak off test last night and whilst the jugs were filling evenly ish after only 5mins pic attached. The rough idle vanished ?? What or why would that happen. I followed the return pipe and found a little valve or connector under inlet manifold?? I've got zero fault codes on this car which leads me to thing an injector is leaking fuel overnight into the cylinders. It's just puzzling me and I'm already out of pocket and at a massive loss. Any help is very much appreciated