wed/fri and sunday i think? ive found getting there early (at 6) on friday is the best bet to get more runs in, as they only allow muffled cars. on wednesday you get rocked with unmuffled car time trials...also i see you have an xi, you can probably brake launch to 2500ish no problem and still grip - try it out!
2011 328xi BSM/Black
2002 325i/2007 335i/2004.5 A41.8T