(2) At any time before the return date specified in an investigative demand, or within 20 days after the demand has been served, whichever period is shorter, a petition to extend the return date, or to modify or set aside the demand, stating good cause including privileged material, may be filed in the appropriate court. [1971 c.744 §14; 1973 c.235 §3; 1977 c.195 §6; 2010 c.94 §3]