muffler

hi I have an Opel Astra G with a single exit exhaust . Can I change it to a duel exit exhaust?? will it affect my engines performance? If I do this do I use a centre dual out muffler ?????

Hi I'm a beginner to tuning cars and I was thinking to start at changing my muffler . Which kind of muffler can I get for my opel astra g for a loud sporty sound???