Afternoon ladies and gents, first time post here.

I've been riding this bike in China for the past three years or so, and after common sense kicked in and told me getting a bigger bike would be pointless here I've decided I want to run som modifications on the one I have.

Specifically I'd like to mod the exhaust to both make it louder, as a safety precaution, and get a bit more performance out of it, but as someone who's never modded a bike in their life I really have a lot of questions I need answered before I start.

Does anyone have any idea what dimension pipes would be ideal for this bike? I don't want tho lose performance due to the common local mistake of getting something too big and loud.
What, if anything, do I need to do with the fuel injection system?
And last, but not least, where in the Chengdu area is a good place to get this done?

Thanks in advance, guys.