i would go for a 4-2-1 one piece, 2 piece is easer to install though. 4-2-1 because if you think about, ill explain this with air and a pipe. air goinging into 4 slots then being pushed into 1 emedilty is quite hard, but going for 4 slots down to 2 then 1 would make your car breather better. thats how i take it.