Still No Dice

[Our03z4]

Update on my 08 Z4 3.0si coupe. I've been having a lurching feeling under 3k rpms, bouncy rpms on start up and sometimes the car doesn't want to up shift 4th to 5th. Shifts in manual mode fine but still has the lurch. Drives fine if I keep it under 3k the whole time but as soon as it goes over, game on it's been triggered for once I go back under 3k rpms.

I took the car to the bmw shop and it had no codes. They recommended a trans flush, filter, pan, and seals, also did a diff fluid change. $900 later still broken. So I thought maybe plugs and coils, changed them, still broken. Maybe it's the vanos solenoids, cleaned them, still no dice. Ran injector cleaner, no help. Checked the hose clamps and for breaks in the intake with no issues found.

Please any advice at all would be a huge help! At this point I'm pretty ticked at myself for buying this. My E85 roadster has been great but this one is a whole other beast and not in a good way...

[wonkydonkey]

1. What gearbox is this?
2. Is the idle lumpy when the gearbox is in Neutral?
3. Is it possible that you missed an air leak in the induction system?

I don't know if VANOS issues always throw error codes - can anyone confirm that? And what engine speeds/throttle openings bring VANOS into play? Would that coincide with the 3,000 rpm trigger being described here? DISA is more like 4,000 rpm.