Engine Misfire: Rough Idle, Power Loss

Hi, I have an AFN (Automatic Fine Navigation) with the following problem description:

The engine initially exhibited intermittent misfires at idle, accompanied by smoke and unburnt diesel.
Using VAG-Com, it was observed that the start of fuel injection varied significantly when the engine was misfiring, but the values in the idle speed control system appeared to be very good.
Starting behavior, both when warm and cold, is very good.

The timing belt was replaced, approximately 2000 km ago. Initially, the error pattern was the same, and it has progressively worsened to include poor starting, severe jerking with significant smoke development up to approximately 1,500 RPM, and then running smoothly above that. The fuel injection looks relatively stable now, however, the idle speed control values are now very poor, ranging from ,9 to -1,9.
I completely replaced the injector bodies with a brand new set, because I wanted to rule out a faulty NBF (although the symptoms don't quite match, as there's no hesitation at higher RPM), and I was also concerned about the LLRR values.
The initial symptoms remained the same, but over time, a loss of power developed. Now, the engine is running so poorly that I'm no longer willing to risk a test drive.

Since I can rule out the fuel injectors, as the distribution of values in the idle speed control is independent of swapping the injectors, I would like to know if this phenomenon could be related to a failing EGR valve. The engine doesn't produce soot or blue smoke at higher RPMs, and there's a slight oily smell in the exhaust, which initially makes me hesitate to think about a compression loss, but tests will follow.

It should also be noted that the coolant temperature rose relatively high twice, which was not critical but unusual. Also, the engine speed increased once for no apparent reason, accompanied by significant smoke, but this phenomenon is no longer occurring.
I briefly thought about the turbocharger, but it's too new, or maybe a hole in the piston, but if that were the case, why isn't the error code showing up anymore?

The diagnostic trouble code indicates a problem with the G71 intake manifold pressure sensor, but this likely only explains the loss of power, not the misfiring and smoking.

I would really appreciate a brainstorming session. Thank you.

Unfortunately, it has been discovered that cylinders 2 and 3 have significant scoring, while cylinder 1 has slight scoring, despite no loss of compression. Typically, all the scoring is located on the walls between the pistons. Is there an explanation for this? For example, could it be due to higher temperatures?

I was told by a cylinder grinding shop that there is a third oversize dimension available. If so, which manufacturer offers it?
Mahle, for example, only manufactures sizes 79.51, 79.76, and 80.01. According to the forum, there is supposedly a size 80.51 available, but from whom?

Thank you very much.