If it has a nice burble when ticking over your sorted mate, you don't need a big loud rally style exhaust on a 1.0 or a 1.2 it just attracts attention. Thats my thoughts anyway.
I thought Sebrings gave a nice ticking over deep tone?
Also wait a couple of weeks or so - When I first put mine on it sounded crap, after maybe a month it started getting deeper.