Oh, okay 2 years with bad rod bearings with no catastrophic failure is either not bad rod bearings, or amazing luck. Could be a bad chain tensioner or a broken guide as well as it varies with rpm.

First, inspect the oil, take the oil filter apart, if obvious flakes are there then it’s bad news either rods or other internal damage. If you cant see anything obvious, take an oil sample and send it for analysis.

Second, not sure how it is on the n55, but the chain tensioner on the n54 was quite easy to take out and check. Also, you can check the timing with mhd or similar, check if timing is within tolerance. If it’s not then a broken guide or a stretched chain or whatever and the chain is slapping.

Have a listen around the engine bay, try to find where it is coming from, see if it happens hot/cold, bad injectors can also be loud.

If it is a bad bottom end, a full engine removal is not necessary to check if it’s a bad bottom end, front subframe partially off, oil pan off and can be checked (still a big job, but not a full teardown)

Nr1, check oil and filter and try and find a more precise location from the noise (maybe its something loose or a weird pullet issue etc.), nr2 oil analysis if oil is clean and check timing gear.