I have an '06 GT on order and was assuming I would mod the exhaust. I have read several places the stock exhaust on the new GT's is pretty good, so I am wondering if I should just leave it alone. A penny for your thoughts!
I love the stock exhaust and wouldn't change it for anything. On my blown '86 GT I had several different aftermarket exhausts (Flowmaster, Bassani, Dynomax, Mac), and all of them had too much drone and were raspy inside of the car. Outside the car they sounded incredible but I never got to hear the good sounds unless I propped the hatch open with a box--which I actually did a number of times.
For me, the stock exhaust is perfect--you hear it when you're on it, and it's fairly quiet for cruising. Also, unlike the Fox bodies, the stock system is 2.5" diameter and mandrel bent, so you don't really need to change it for performance reasons either.
I really like the sound of the stock exhaust. As mentioned earlier, there is no drone - it sounds great when you get on it and at WOT - and is pretty quiet when just cruising 70 or 80 mph. Fine with me for now, but I'll wait a couple years before I go with some sort of variance with Magnaflow. Will be nice when the prices go down a bit.
My 2 Cents.
To me it sounds pretty good. Has a nice note when you get on it and at cruise zero cabin drone. I've had a couple people comment that it sounded like aftermarket and ask what it was.
Eventually I'll have the entire exhaust train changed out. For now the stock exhaust is plenty good enough.
I really like the stock exhaust sound, but I may do an axel back magnaflow set just to add a little more deep end growl. Unless you plan on mod'ing the sheet out of it, stock is great.