a few years ago a mate of mine had an e30 with an m50 2.5 24v lump in there. it felt ok but it was a lump that had been sat around for ages.
after a few oil changes the oil filters werent coming out as scary looking.
after that we made up a concotion of diesel 5w40 fully synth and auto gearbox fluid for the engine (both fantastic engine cleaners). i think due to the improved oil pressure and the cleaning effect the car had a far more noticable vanos "kick" (obv not neck breaking like vtak) but it showed exactly how dependant the system was on oil pressure. we were even able to compare before and after output plots and visually the difference was huge