From memory I think EcoTune have some options for the B48 engine so might be worth giving them a call or checking out their website. I can't comment on them though as I've never used them.

In terms of exhaust you'll probably want to go for a full 3" system if you're chasing performance.

You may want to look at a sports cat but if you're tuning beyond the standard catalytic convertor then you'll probably want to upgrade the cooling as well.

After that it's just a case of deciding how many (if any) resonators you want and whether you want to go for a particular brand or a local exhaust shop if you know of one.