Sonoma is difficult cos its very bumpy but requires some med-high speed direction changes particularly in sectors 1 and 3.
Try a fairly soft spring rate to cope with the bumps and then add med to high roll resistance (sway bars) and soften the front slow bump and/or rear soft rebound to speed up the weight transfer that will allow you to make the high speed direction changes.
Fine tune the tyres and front/rear balance to your liking and that should be a good place to start
Last edited: Mar 11, 2016