There are no such a "numbers". Turbo boost is determined by many factors, including, but not limited to engine load %, incline, ambient temperature, air mass inflow, fuel quality, etc. It's determined basically by a map, that's stored in the engine ECU, but it's also corrected with several other variable factors - some of which I mentioned previously.
Anyway, even if it existed, why would you want to know the "boost number"? If you want to check whether your turbo is working as expected, you don't need to know any such "numbers". You only need to know what turbo pressure the ECU has requested, and what it was actually getting/sensing. Both of these values are readable and loggable through VCDS in the engine controllers measurement blocks.
lol. Your telling a guy with 25 years of diesel experience ( I used to run a diesel performance shop with our own dyno.... now I just have a online store, as I am semi retired ), and your telling me there is no such thing. Thatís funny. I have built & worked on diesel engines that have made as much as 1900hp & 140psi of boost out of a 5.9L Cummins. My personal daily driver makes just shy of 700hp & 54psi with twin turboís & 23mpg. Our other VW ALH 1.9L TDI makes just shy of 200hp & 350ftlbs & gets average of 59mpg. I control exactly how much boost they make under max load & at 65-70mph. Iíll get off my high horse now. lol
I know my wife's Touareg turbo is working right ( no worries & no issues & I have the Vag-Com & other software to be able to see what the ecm is requesting & what the actual is ) I just simply am surprised at how high the boost reads with low load, flat ground & 65-70 mph itís running. I wanted to see what others are seeing on stock & a bonus would be a tuned one. There is no need to run this high of boost, specially at cruise with low load (egtís are not an issue, nor power ), as this high of boost simply is a restriction at low load & hurts fuel mileage. This can be changed with a custom tune easily enough. I donít follow the masses thinking the higher the boost the more power your making, as I know itís somewhat the opposite. Boost is more of a measure of restriction & or load than anything else, & can be manipulated to make more or less by the position of waste gate pressure or vacuum or the vgt in this case. If the Touareg's 3.0L was making approx 5-6psi at 65-75mph, instead of high teens, the fuel mileage/efficiency would go up quite a bit.
Back in the day when I first started playing with our 1.9L ALH TDI & posted a 175hp dyno graph with stock turbo on the TDI Club, the boys said it must be a dyno graph of a gas engine. They said the stock turbo would blow up producing that much boost.... lol, nope, in fact I made the turbo make less boost than MAP & I smoothed out the power ramp (easier on everything, specially the turbo) & carried it high for a lot longer than others were doing, without any turbo flutter, as I controlled what the turbo was doing. They said it couldnít be done & I did it with a $35 manual adjustable boost elbow, feeding in a small amount of boost in to the vacuum controlled ALH waste gate line. All the other guys always complained that their dyno graphs show & could feel the boost go up & down at WOT. That was because the ecm/map would see too much boost (vanes fully closed) at WOT & would request less vacuum to open vanes & lower boost.....than it would see too low of a boost drop for the MAP & start the whole yoyo affect all over again. A few tried my simple mod & they seen the light, that sometimes thinking outside the box can be beneficial. I simply let the turbo breathe & in effect made more efficient power, with less boost.
Itís all about letting the engine breathe & the turbo is the biggest factor in this. Try flowing say 100cubic meters of air at say 100psi of tank pressure, through say 10í of 2Ē pipe & try the same with a 4Ē pipe & see which is faster at emptying the tank & what the psi is at end of the discharge pipe. Larger it is the more flow you will have & at a lower psi.
I try not following the masses all the time, as the masses get what they get because they donít know any better. The tuner says this is the best ( whether this is VW itself or a custom tuner ) & the masses say ok. Donít see much for fuel gains on these tunes, so Iím asking myself why. Iím thinking the engine isnít breathing up to itís potential because the vanes in the turbo is restricting flow & Iím also seeing lower than usual fuel timing on graph. This can be tuned out of course.