Stock exhaust manifold vs rb header.
 

Hey I was looking into getting a racing beat header for my 1990 s5 gtu. The racing beat website said they do not recommend the header unless your car is carbeurated, as the gains will be negligible. Does anyone know why it is. Instead they recommend stock brick with a cat delete. So I bought the presilencer cat delete pipe from rx7.com and decided to run the stock brick until I get a turbo2 manifold. Does anyone know why the rb header wouldnt work well for an fuel injected fc vs carbed?