Invidia Down Pipe "Australian Spec" w/High Flow CatINVIDIA CATTED DOWN PIPE The most restrictive component of the factory exhaust system is the down pipe which begins right after the turbocharger. Invidia Exhausts use a open bellmouth design to completely open up the exhaust flow path out of the turbocharger. This open bellmouth design combined with a larger pipe diameter and smooth bends allows the turbocharger to exhale exhaust gases with fewer restrictions and turbulence. Because of these reasons,