MAC Ford Mustang V6 4.0L 2005-2010 2½" Stainless Steel Off Road Pro Chamber to MAC Short Tube Headers or Stock Manifolds MAC's 3 piece Pro Chamber Design allows you go from Street Legal to Full Race in just about 1hr-2hrs. The MAC PC2605 can be bolted to the Stock Catalytics or the MAC Off Road Legs. This is a Great Up Grade for the Weekend Racer. Keep your Mustang Street Legal when driving around town and on the weekend go all out with a Off Road Racing Exhaust System on the Track!