2007-12-05ALERT! Before you replace your suspected failing brake booster you might want to change the o-ring seal between the master cylinder and booster first. I have seen more than one expensive booster replaced when it was only a $2.00 o-ring. If your engine is producing good vacuum to the booster but your brake pedal still feels hard then at least check this o-ring.
107 114 115 116 123 126 Brake Master Cylinder to Booster O-ring Seal