Which exhaust system of these 2 would make more hp with an NA?

http://www.racingbeat.com/RX7-1986-1...sts/16420.html
or
http://www.corksport.com/corksport-p...st-system.html (2.5'' piping)

 

There is little power to be gained from a catback system, so I don't think any small different should be the deciding factor. The RB system is widely used, sounds great, and will keep noise levels tolerable. The Corksport catback will weight a little less, and also be significantly louder.