would the tanabe touring give me more power than borla for my GS3? Also which exhaust gives you the most power

No muffler is going to give you any more than 2-4, maybe 5 hp.

Yes the Tanabe will give you more power than the Borla. The Borla is only a rear section, it retains the majority of the factory piping. The Tanabe is a "cat back" which means it totally replaces the exhaust from the catalytic converter back. The piping that Tanabe uses is larger diameter and smoother than stock which allows for it to make more power.