I guess I'm just one of those stubborn people. If I'm not mistaken, only Borla makes a 2.75" version for the 13-14 GT. I'm not too worried about performance right now. In time, I eventually want to go with a Roush phase 1 supercharger, which is why I wanted to upgrade to 3 inch pipes. My car is only lowered one inch, not sure if I'll have scraping issues. I'm going to have to think about this a little more. Who knows, I might even go with another brand, although I have to admit, I love Borla exhaust systems.
I have the 2.75 for the 13-14. I mean those pipes are plenty big. But its up to you..
funny thing is that the factory h pipe is 2.25 lol. I wish someone made a replica 2.75 inch boss style h pipe. I tried the mrt 3 inch one and it just wasn't aligning as good as the factory one.
and my friends was scraping on the diff and axle with 1.75-2 inch drop.