Like I said earlier dont test the Factory Headers Exhaust Manifolds against that over the counter stuff. Even TTI and Hooker are made to fit first and flow second. Even with the factory header it does not work with every application or variable that a RB-B Motor can be use for. If you are looking for a cheaper exhaust that works ok use the headers that every speed shop sells. The Max Headers looks cool and works real well. Custom built race headers and exhaust system cost money. Go what every way you like,but research before you buy any of them.