I dont know much about exhausts myself...but I was wondering If I took my car to the exhaust shop and just get a 2.5' pipe exhaust (no cat) all the way through and buy one of Rock's Greddy exhaust weld on, what would be the difference than just spilling out the $500 for the Greddy cat back. Would it sound different? I want that deep throaty tone thats also loud (like this wrx sti i saw). and i also plan on turboing my oz rally soon so thats why i'm going with 2.5 instead of 2.25.
What do you all suggest?

 

Personall i would suggest to wait until after you turbo the car to do the exhaust. Your bottom end will be terrible with a big exhaust, but not with 2.25 or even 2.5 shouldnt be too bad. Only problem is, you might want to do bigger after the exhaust and wasted money on doing it over. Piping is piping as long as the welds are done correctly and the fit is stock. Also, mandrel bent. The tone will sound different running no cat, it will be alot louder most definitely, and will not sound like the STI motor whatsoever. It's a friggin porsche motor.

As far as the difference, tone, money spent, not having a true name brand, and what not. But, if you can get a custom exhaust with awesome welds, and mandrel bent piping to fit stock for half the cost, i would do that instead. Good luck!