2010 BMW 328i N52 engine, 250,000 miles.

Engine runs very well for milage.

The engine lightly knocks/pings under light to moderate acceleration.

Been going on many years and very slowly getting worse. I used to be the only one that could hear it.  No longer a subtle noise, but also still not really loud.

It's definitely detonation.

If you put your foot into it quickly, you might notice a pinging at first, but then the engine will accelerate aggressively and smoothly with no noise. (putting your foot into it quickly usually gets the loudest pinging, but only briefly before the engine accelerates smoothly).

Or when releasing the accelerator pedal, it might briefly knock.

Or as the car cleanly accelerates, it might briefly knock immediately before and/or after the transmission shifts.

No codes with a fairly decent scan tool.

Have replaced with no difference:

Spark plugs.

Coils.

Fuel injectors

All O2 sensors.

Air filter.

Mass Air Flow Sensor is original, but was tested with an aftermarket sensor with no difference.

MAP differential pressure sensor.

Timing chain (re-timed engine)

VANOS solenoids.

Valve cover (smoke tested/no obvious vacuum leaks)

Have ran tons of fuel additives to clean combustion chamber. Lots of highway miles.

Always use 93 octane.

HAVE NOT REPLACED:

Knock sensors.

Various intake gaskets (but seems to pass a pretty good homemade smoke test).

I'm afraid to test the compression.  :-(.   Could low compression cause these symptoms? Engine runs smooth.

Have not tested fuel pressure, but the engine runs very well except for light knocking during light to moderate acceleration, during abrupt movements of gas pedal in both directions, and before and after shift points.

What are your thoughts?

This engine is tricky because of valvetronic, which is throttle by valve lift control.

VANOS system seems to function correctly.

Thank you kindly.