After living with this illuminated needles and plasma dials combination for a while, I have found that the needles are too bright for my taste.
Even on minimum on the adjuster.
So I went back in and soldered the small rheostat (supplied) in series with the OEM adjuster.
I adjusted this rheostat to give me my preferred range of brightness with the OEM and put it all back together.
Result - now I have a more restrained needle illumination!