On e90post tons of threads on this. I wouldn't call your agent though.
1) If they you are covered be sure to get it in writing, few cases of people getting burned by this.
2) Carriers have dropped people for asking.
3) There are track specific policies out there based on total value on your car.
4) Read your policies carefully, most of the major providers have clauses that include "high speed" and on a dedicated race track for exclusions.
5) I'm not a lawyer, if in doubt get profesional advice.
2008 E92 M3 Jerez Black,DCT,Fox Red ext,Prem,Tech,19", ipod/usb, CF roof and trim
2010 E91 328i Space Gray,Black int, M sport, most options
2007 Montego Blue 335i (retired)