i have an s4, and i read how the 5th and 6th ports are activated by back pressure.
then i also read on here that if i were to get the racing beat presilencer they should still work.
and i currently have the streetable RB header (http://www.racingbeat.com/FRmazda2.htm)

i ws wondering if i install the header and get the presilencer will my ports still work normally or will there not be enough backpressure for it?

 

If you get the header and presilencer then they will work regardless of the rest of the exhaust. You obviously still have to have the split air pipe hooked up, though.