I love CORSA, too. And, still may put one on having just put one on my son's 2004 Silverado 5.3l. The sound is awesome with no resonance. But, while I know catbacks are not giving to give major hp gains, the CORSA on the GTO is 2-3 at the wheels per an email exhange a couple weeks back with them. The merging from true duals to single pipe reduces the amount of power they can make. I am taking a look at Borla but, still concerned about resonance. Ultimately, I may say the heck with it and just go with CORSA for fit, finish, looks and sound.