Been after these for a while and I finally had the opportunity to pick these up over the summer of '11. Bar none, one of the BEST decisions I've made in modding my Mustang so far. The sound is perfect at idle or at WOT an really gives the mustang a personality. The sound is significantly louder than any clip you'll hear on the web, but not obnoxiously so. When you get on the throttle, they roar, and when you don't, they are only marginally louder than the stock exhaust. I've had the opportunity to listen to the GT500KR at Carlisle this past year and these sound exactly the same (and they should, because it's the same model of exhaust). Installation had me a little worried as I was afraid I'd need to worry about alignment and all that. It was completely unfounded. They lined up perfectly and it's practically dummy-proof. In fact, the biggest challenge was getting the stock ones off as there's a bolt above the muffler body itself and you have to be a bit of a contortionist in order to get to it. However
Did a lot of looking and listening ... and the money on these was very well spent. Easy to install, great looks and most important, sounds OUTSTANDING!! Not too soft, not too loud (50 state legal) ... works very well on the 4.6L and once warmed up, no annoying popping sounds like other mufflers.