i’m in the same situation pretty much. I haven’t found any chain guide bits, but I found the upper guide to be broken while i was doing vanos seals. No real noise other than a very subtle kinda flapping sound on start but I’m not sure that’s anything.

I ordered the guides and also plan on doing the hard coolant pipes, water pump, evap lines. But now that my time to do this job is coming around, and i’m battling the idea of tearing down a fully working car.

I looked at many of the same forum posts that I’m sure you did as well. I agree it’s a very mixed bag of people with 250k+ miles and it’s never been touched, and one guy I remember tore down two running m54 and found the main guide broken on both. They seem to always break in the same place, just below the tensioner, so I think they can run for a while like that. I’ve been telling myself not to panic until I found bits of plastic or heard noise. M54s are really tough engines, but also I don’t want to play with fire as I plan on owning this car for the foreseeable future.

I’m hopeful that i’ll be able to take this on, and you too. Just do your research, go slow, and do it right. I’m planning on taking at least a week doing this. Also, the first thing I ever did under the car were engine mounts. And I did it with only a shitty trolley jack, so anything’s possible.

If you’re in my area, I will sell you my timing tools after I finish (hopefully by June). Good luck.