I love the sound of the Greddy EVO 2, if I weld and run my own custom piping from the downpipe, then get an EVO 2 muffler (if that exists) would it sound just as nice?

 

Without changing the headers, there are only a few key variables that significantly change the sound of the car.
1. Material used.
2. Thickness of material used.
3. Sound attenuation type ie: baffles or perforated tube
4. size of attenuation apparatus
5. Resonator or no resonator

So, the sizing is mostly volume, and everything else is small in how it can change the sound of the note.
if you use the same materials, same thickness, and same muffler, the sound is for all intents and purposes going to be the same.

 

I can't say it will sound as "good", just that it will sound similar if you use the Greddy resonator and muffler. Personally, almost all fartcan-like mufflers for Civics make me feel sick inside.

I'm guessing you're hoping your turbo setup will sound somewhat close to an NA setup will with the same muffler. It won't even be close. It will be quieter, lower, and less annoying than a NA Civic normally does. The turbine, cast-iron housing, and high-mass pipe/cast manifolds all make a huge difference on sound.

To give you an idea, an Evo 2 on a stockish NA motor (header and cat) is about 2x as loud as a 3" turbo-back exhaust with 1 resonator and no cat.

 

My stock exhaust is falling apart and I liked the sound of the EVO2 from the looks of it.. Not too loud or raspy in my opinion, it will be n/a GSR swap until further notice, lol..

Should I run from the cat back? I should keep my cat I think.. Legally. Should I use aluminum or something more heat resistant? I like how light aluminum is.

9bells: Have you ever done a full exhaust with custom muffler (no fart can) for a civic or 4 cylinder? I don't want my **** to sound stock is all..