Mazda Motor Corporation is extending the warranty coverage for specific repairs for vacuum power brake booster units on 2007-2013 CX-9 vehicles produced from October 24, 2006 through April 26, 2013. The warranty for this repair will be extended to 7 years (84 months) from the original warranty start date or 90,000 miles, whichever comes first. If a vehicle has already exceeded 90,000 miles or 7 years, this coverage will continue through March 31, 2015. Some vehicles may exhibit a condition that the brake pedal is harder than usual to depress. An air leakage (hissing) sound may be heard from the driver-side foot area during braking. Dealers should install a new, improved power brake unit. Please refer to Attachment I for details.