[brzaapi]

I would defer to CSGMike on this, but it is my understanding that in NA form the TP (elimination of the OEM Cat) is by far the best bang for buck. It was worth it to me.

However, items like the header/manifold and cat back systems seem to help more with response and fleshing out the power band, more than giving big peak gains. But, I bet Mike could add more depth to the S2k bolt on mods.