6speedonline has more action than rennlist, but I agree rennlist seemed like roadfly back in the day of the e46 m3 but with a modern bulletin board. However all this being said I found myself hanging out more at 6speedonlinie. I also joined renntech.org when I had my 997S.
2013 M3 Coupe-MR/BLK ZCP, ACM test pipes, BPM Stg2 dev. tune and Megan catback, more to come
Previous rides: 2011 M3 Coupe-MR/Blk
2007 Porsche 997C2S Speed Yellow/Blk sport seats
2004 BMW M3 Imola/Blk