I don't drive mine much slower on the road, and you can see from my fuelly link that I'm getting 19 ish too, not making it any easier for you am I ?
It was good to chat and glad you liked the pax laps
I've been looking at better brakes, the engine feels unburstable and the chassis is great but 10 mins of that and they were grumbling badly,
I had e91 330d and 335is then an Audi S4 mapped and pulley changed to 420 and nothing feels the same as the M3, and only the 330d did better than 20mpg
And you've now got the green light at home too....