3 is better then 2.5. if you had kr it might be gone with it. that u bend is a choke point. just removing that helps, so a larger pipe will be better.
be best to buy a new rear o2 sensor too, the old one will put up a damn good fight, and likely not come out. iirc them zzp dp's moved the o2 bung further away and you need a extension harness too.