I plan on upgrading my exhaust on my 2012 GT with either a JBA or Heartthrob H pipe and the GT 500 axelback mufflers. Question is, JBA has a 3in to 2.75 and a 3in to 3in H pipe. Which one would I need for the gt500 mufflers? Also, would this set off any CEL's? I'm keeping the stock cats.