If you get a cold air intake and lets say your horsepower is increased by 5. If you then get a catback exhaust would your horspower go up 10 b/c you already have a CAI? Or if you just got the cat back exhaust would you get the same horsepower increase as you would if you do not have a cold air intake. In other words as you start to add more bolt on performance mods does the hp snowball in a way and increase proportionately w/ the mods you already have, do you get more horsepower than you typically would if you just had one mod.
The cat back system would benefit more if you have the necessary upgrades to complement it. It's like anything, you have to have a package that works well together, a chain is only as strong as its weakest link.