Alright, update time!
2 days ago I went for a few highway pulls to check whether my pump has failed or it's just unable to exceed 120 bar under 5k rpm. Floored the car in 2nd till 7k, shifted, dropping to 5k and repeated it in 3rd and 4th. Well what do you know, the car ran just fine, no hiccups, no fuel cuts, no nothing, 130bar just fine.
Yesterday I took off my pump, inspected the cam follower and the cam lobe. The follower was replaced aprox 4k km ago and has started to wear out in the normal spot; the dot in the middle. Cam lobe looked fine and paired up with the usual follower wear, I crossed a "failed camshaft" off my list.
Also yesterday I sent my pump to a local shop, Vis Motorsport, to be completely cleaned and rebuilt with uprated parts for 175 bar fuel pressure. Today the shop messaged back that they rebuilt my pump but also wanted to let me know 2 very important things.
One, my engine is quite dirty inside, which I was already aware of. Whoever owned the car previously neglected the oil changes, or only did oil changes in 30k km. How does he know my engine is dirty? Well due to the amount of buildup in my HPFP! He said my pump was one of the dirtiest that he has ever worked with. He recommends I take off the oil pan, get it cleaned, clean the oil pickup line, replace the oil pump as it's a ticking time bomb and also get a freewheel to disable the balance shafts as I have a high chance of both the oil pump and the balance shaft toothed wheel failing. Both of which could be catastrophic for my engine.
After I mentioned that people on the forums said disabling the balance shafts would cause extra vibrations and noise, he said that's nonsense and anyone who is having those issues either has worn out engine mounts or uses reinforced sports engine mounts.
He also said I should flush my engine at least twice and start using performance oils, such as Motul 300V 5W40.
Two, the surprising bit, as I haven't seen this mentioned anywhere whatsoever. Apparently there are 2 generations of fuel feed lines that lead to the pump. The first generation which uses a banjo bolt and the second generation which uses a rubber hose to connect the metal fuel pipe to the HPFP. In both cases, there's a fuel limiter that limits the amount of fuel that can pass through, making your LPFP work way harder to feed your HPFP. He suggest drilling out this limiter hole to 5mm. This will help preserve your LPFP. He said either drill out the limiter hole or fit the newer generation fuel lines and drill out the limiter in the bit that comes screwed into the pump.
In the case of the older fuel lines with the banjo bolt, the restriction is in the form of a cast iron shield with a 1.71mm hole in it on the metal fuel line (pic 1). In the case of the later generation fuel lines with the rubber hose, it's mounted directly into the pump (pic 2).
I've asked him about the new generation cam follower retrofit kit, which ads a spacer to your pump and lets you use the newer roller based cam follower. He said this does more bad than good. It modifies the pump opening/closing times, which messes with the fuel pressure regulator ontop of the pump. He said simply keep the stock follower as that's what the engine was designed with and keep track of how much it's worn out.
Tomorrow I'll be fitting the rebuilt/uprated pump and also drilling my fuel limiter out. I'll go for a few pulls to see if anything changes and if stuff works now, I'll put back the aggressive fueling map to see if stuff finally works as it should. Afterwards, I'll be doing an engine flush and an oil change as I've been half a year on my current oil already.
