Does anyone have any suggestions for modifying performance or anything beyond stock OEM for the b34f n/a exhaust system?

I have sided with, stick stock... I am preparing for replacing the exhaust manifold and header down pipe with OEM. Wondered if switching to, perhaps, a turbo cat-converter could be a benefit, or what to do with the exhaust system to enhance performance and create a sweeter tone to the sound of the exhaust, from the down pipe backwards.

Thanks, hope this is not too wrong to ask.