alright i see alot of people here talk about replacing catbacks.... couldnt i just go all pipe 2.5 inch all the way and do the same thing..or do i need the cats on i have a n/a s4

 

On the S4 the cats are needed to make the 5th/6th ports function. By removing the cat and not figuring out a way to make those ports operate your fc will lose some top end.

You can do a search and see what other people did get those ports to work with out a cat.
If it were me, I'd keep the cat and try to find a high flow.