HKS Spec L update now it’s been on for 4,000 or so miles.
It has settled down a bit, it sounds bassier and smoother. It is loudest at 3k, but having to do some motorway miles in the UK yesterday and today (6 or so hours total combined) I’d genuinely say at its loudest at 3k, but most of the time it’s not as loud as the road noise, - yes you can hear it but it’s no more intrusive than the PS4 roar (motorways M40, M25 and M3).
Occasionally you get the blessed relief of road noise on a flat smoother bit of fresh tarmac, at that point I’d say its louder but (to me at least), not unpleasant.
The only time I found it a bit boomy was on a very long slow hill descent where I was coasting in neutral, bang on 3k (Remenham Hill descending into Henley for those local). It seems constant 3k on overrun is the Achillies heal, but luckily that’s a niche occurrence. - probably also impacted by the fact that I was going fairly slowly on fairly smooth road, so road noise was minimal.
It was quite quiet with the cruise set to 70, seemingly quieter than me manually maintaining 70. Once you are in the 80 or so zone you are clear of the 3K rev range it is fairly modest anyway.