New tyres will make a big improvement, the best tyre out there is the PS4S for road comfort. THE Pzeros are pretty good too. They just need to be new and up to their half life, after that, road noise will be annoying again.
Insulation works wonders as well I insulated the M3, 4 years ago and de-insulated a month ago.
I wrote about it here:
https://f80.bimmerpost.com/forums/sh...09&postcount=4
You need to use a combo of butyl)or Dodomats roadblok, which is very heavy stuff on the bottom wheel well panel and on the rear wheel arches and then thinsulate all around the rest of the rear, boot floor and the side panels. Thinsulate is very light and can be used freely.
New tyres and this will make the car very quiet.