Confused about 3" Catback

[GreyCobra_03]

Alright, I know this topic has been beaten to death, but after reading this forum for 3 months now and watching different people's mod list, I have noticed that alot of people are putting JUST the 3" catback exhaust system on their cobras. I haven't seen a thread explaining why this would be beneficial, isn't the stock H pipe where the diameter is necked down to 2 1/4 in? So what would be the benefit of replacing just the catback if the exhaust is so small farther up? With the list of mods below, what kind of gains could I expect with just the catback vs. the whole 3" system?

I'm very new to Modding, feel free to flame me, also, I did some searches last night, and couldn't satisfy my curiosity.

 

[bender460]

I think some are planing ahead. for me when I get a 2.93 pulley and chip and long tube headers add a custom 3" X pipe thats when I'll see a good gain with the 3" catback.( one less thing I'll have to change). But at the same time I think some people are not gear heads (like myself ) and just think bigger is better no matter where it is.Or they just like the sound of it. Or just like to say they have a 3" exhaust.:shrug: On a stock 03 I feel there is no gain from 2 1/2" to 3" catbacks. That may change with a o/r xpipe however. I wish I had dyno close to me.