There is a code stored if VANOS pressure drops below the setpoint (not sure what that is), but if the car doesn't have that stored, you are probably ok.
The actual test procedure IAW with ISTA or DIS connects an external pressure gage to the VANOS system at the silver "T" banjo fitting just below the forward end of the intake plenums, aft of the fan cowl, where it branches off to either operating unit. The engine is run and the pressure is monitored using this external gage. I believe BMW currently uses a pressure transducer connected to an IMIB (Integrated Measurement Interface Box) attached to the ICOM diagnostic connector. But, this doesn't do anything special, I don't think, so you get the same value using a manual pressure gage with a range of 150bar. The whole point is just to be able to read the actual pressure instead of using the built in pressure sensor the car uses.
If this pressure is low, you have a few possible causes, but the actual fixes are limited to just two: the VANOS high pressure line (the one which had a recall for early vehicles) or the VANOS high pressure pump. It's hard to say what causes the pumps to fail for sure (no one has donated one for autopsy yet
and I'm not keen on dissecting mine for the hell of it), but with all of the speculation of "swarf" contributing to VANOS solenoid failure, I'm sure running metal pieces through the equivalent of a five cylinder radial engine isn't good for it. It stands to reason these could be rebuilt somehow though.
However, if your only symptom is noise, I would recommend performing the VANOS system test in DIS or ISTA and then the ventilation (bleeding) procedure a couple of times and then reperform the VANOS performance test. The ventilation procedure takes about 18 minutes and makes some funky sounds as it goes through its paces, but some people see improvement after. The repair procedures in ISTA reference noise on startup after component replacement being normal until the system is fully bled.
Given that the system uses engine oil, it stands to reason that oil quality (i.e. age) may have an effect on system performance as well and that is mentioned in the VANOS solenoid test procedure discussion in ISTA. It implies that oil which is in poor condition can skew the performance test.
So, if you bleed the system and the solenoids current and stroke times come out in spec, I wouldn't worry too much about it.
The car is usually pretty good about recording what goes wrong, just not great about telling you it recorded anything.