With 180k+, and 18 years on the stock harmonic damper, it was time for replacement. Splurged a bit, and got the VAC motorsports version by ATI. I am a sucker for heavy duty upgrades.
While preparing and researching, I saw some places talking about the alternator pulley. Some links:
https://www.e46fanatics.com/threads/...d-info.806821/
https://www.youtube.com/watch?v=9beaAjKLBnY <- good voice on that dude
https://www.youtube.com/watch?v=gXa384YJdL0 <- explainer video
I decided to give it a go. Yes, the M54 is already smooth, but this can't hurt.
This tool helps with the installation: http://www.metalnerd.com/catalog/pro...5e586d88a2e97d
Per the videos, the pulley increases the alternator efficiency, but it is also 12% bigger, which likely negates that with the under drive effect.
The 3mm bigger radius is easily within the belt's and tensioner's tolerances; I dare say it is plug and play.
The result. I immediately noticed a smoother running engine. Climbs the RPMs faster, too.
Did not check fuel economy yet, but I saw a small bump in the instrument cluster; maybe 1 MPG after 1/2 a tank. And I was not gentle with it as you can imagine.
BTW, there is another pulley mentioned here: https://www.e46fanatics.com/threads/...-list.1249269/
That did not fit my car, maybe it will fit some models, but as I had my old alternator out - 12317519620, I compared the pulley when it arrived and there is no way it will fit. VW part 022903119C in the first post fits.
Will post here again if I run into any issues at all.
Maybe someone can install only the pulley and share their experience. I posted two parts here, so cannot attribute the benefits to either of the parts with confidence. The price we pay for "might as well while we are in there".