Decat or 2.5' cat-back system which will make more power, the stock system is already 2' just wonder would I gain any power by replace it by 2.5' or decat? Is for B16A has I/ VAFC and Toda B.

 

from experience stick with the cat and 2.5 pipng from cat back..everyone always told me to get rid of the cat and increase piping size..which i did..and even though it sounded better, i realised after i put the cat back on for my yearly vehicle test..that the car ran/drove/performed way better with the cat and bigger cat-back piping..theres no way that i'd lose the cat again...!