535I 2008 N54 surging light load

[CIM535I]

Need help folks.

I have a 535I 2008. 6 M Went through the engine in 2021 turbo change , Plus 200Kmile general maintenance

I'm getting a light surging at light engine load around 65 to 80 mph.

It is engine load dependent. If I'm drafting It can show up. If it is a slight down grade It could show up.

The gas MPH gauge shows a swing in time with the surging.

If you accelerate it it goes away. But comes back at light load.

IF you WOT it goes away, some times for good.

Never when engine is cold. Needs a good 20 min drive time.
Latest injectors
New plugs 5K
New hoses
New vanos


ANY IDEAS??????

I have a Foxwell NT 510 elite to help diagnose if that helps. Novice user.

My thoughts

Possible cat O2 sensor post cat failure.
Turbo wastegate vacuum control valve failure
Turbo failure
Crack in vacuum holding chambers.
airflow sensor going bad.

If you have an Idea let me know . I have a trip coming up in two months 3000 miles and like to take this car.

Thanks
CM