I think possibly one of the reasons some people hear a more dramatic improvement with the damper while others don't may have to do with how effective the stock insulation / sound deadening is. I know that in 2018/2019, the US models started coming with these cheap sound-deadening 'pillows' glued to a couple of points around the spare tire well, rather than proper tar-based deadening pads aka dynomat (another post-dieselgate cost-cutting measure). When I installed the Helix sub in my 2017 GSW, I supplemented the factory deadening mats in the trunk area with a few extra square feet of dynomat-type pads (not a lot... just a few small pieces in a few key areas where VW should have put more), and also inside the rear deck lid, where VW did not put any. On top of that, I laid down 1/4" foam insulation padding over the entire trunk floor area and I also lined the backside of the deck lid interior trim panel with it. Honestly this all had a much more significant impact on quieting the sound of the rear suspension than the harmonic damper did. I installed the damper well over a year after doing all the insulation supplementation, and I only noticed a very marginal additional improvement... if at all... and the sound deadening and insulation has provided improvement for not only low-speed noise, but high-speed as well.
