535i rough idle at 700-750 couple questions

[an535i]

I have a 1990 535iA (150k mi) with a constant rough idle and I've done everything i can think of to fix it.. first the problem : The car idles steady at 700-750 but at that rpm it feels like its missing a little .. runs smooth at 800-1000, like glass smooth..
now heres what i've checked or replaced:

replaced all vaccuum lines, checked intake tract for leaks / cracks
cap and rotor replaced
plugs replaced (old ones were really white)
spark plug wires @ 0 ohms
valve adjustment according to bentleys
checked MAF for resistance change with movement of flap - yes,
checked tps according to bentley
cleaned ICV and Throttle body with carb cleaner
ICV is buzzing and voltage was good..

Fuel Filter was replaced 20k miles ago
I havent done a fuel pressure test because the car always fires up immediately..




Oh ya and i ran injector cleaner in a couple tanks of gas beforehand..
Idle is just rough no matter what i do..

So is there any thing i have overlooked here?? Or is the next step for me to just dive into my perfectly running 535i (other than slight miss at idle) and pull the cylinder head off ??

Im lost
any help is appreciated..


P.s. Anybody in Sacramento have a MAF I can test on my car?

[netmgr]

i have excactly the same on my 525 M20

idles fine when i rev to 800 but when idling it hunts about and sometimes feels like it may stall

on some days its fine, no hicups at all perfect...

i clean the throttle body usually and thats usually enough to fix it but this time it just wont go away..