Cars always hunted if you try to hold revs at around 900rpm. Needles bounces about quite badly. It drives perfect but this has always annoyed me.
Smoke tested twice and nothing noticeable. Pcv system was renewed beforehand . Wondering if could be some sort of air leak in throttle body gasket that shows under certain load.what about throttle position sensor? Anybody solved similar

Reckon fuel pump is going. Well known for it. Mine went just like this with hunting needle etc. Easy to change. Only other thing could be the MAFF?

if this is the BMW V8, check the second "port" on the back of the OCV valve cover in the back of the inlet manifold. There is an open hose connector which should be blanked off with a small yellowish cup. If left open, it sucks in air, which condenses and causes all sorts of trouble in there.... water in lower elbow on PCV system, usually freezing up in winter time.
And it makes the lambda sensors go nuts wehile trying to regulate fuel/air mixture. You should be able to see such things on a live OSB tester.

regards
heppsen 2017 MB V-Class
2016 Q7 (gone)
2012 FFRR TDV8
2012 Smart Pulse Turbo
1986 MB W126
1965 LR Series 2A
1961 LR Series 2

I will second this as this was my issue but the smoke test showed it Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

Mine does it and has had new MAF, PCV and everything else but drives fine and idles very smoothly.
My PCV ports are blanked off, both of them I think.