Surging under power

throttle body maybe or pcv valve perhaps might even be fuel pump in the tank maybe,, or fuel tank vent valve on bottom of the inlet manifold ,, could even be vanos sprocket live data run should work all that out,

added one maff sensor maybe

I would check the spark plugs and coil packs, Then I would replace the Vanos Solenoids. As you have the N16 engine.
buying one coil pack at a time. Using that brand new one and going along the engine swapping that good one out for another listening for it to even as you drive it each time.
Sometimes the brand of spark plug you run and turn to garbage under higher RPM. Not a problem with one spark plug more like all of them. If the car is not running tip top for the most part.

surging more likely to be a timing chain issue or and vanos sprocket,, need live data run on it see what it doing and when etc, if had spark plug of coil issues it would have misfire counts on live data also surging and misfire feel differently