I just installed a set of Flowmaster American Thunder Classic axle backs on my '12 GT........Phenomenal difference! The car truly sounds like it should now. I've been searching for, and reviewing just about every axle back setup out there. I had the Flowmasters at the front of my list the whole time, but had to give the others a looking over. Finally, I came back to the FM's, and I couldn't be happier! They almost make it seem as though you're in another car all together. The stock mufflers really are POS's...... Anyone else out there have these axle backs?