Any header to axle exhaust upgrades?
 

I'm interested in running the stock exhaust with JDM tips, but would love more power. Any development of an exhaust pipe that is bigger up to the muffler in the works?

I don't think there's any bigger b-pipes available which will bolt up to the stock muffler. Maybe you should just consider to go with a header, over pipe and down pipes instead.

Most of what I've read says replacing the midpipe is mostly for aesthetics and or sound. If you don't care about that and just want the power increase put on a nice header and leave everything behind it stock.