normal means no flow exchange from left to right. XPIPE. means you make a connection right after the downpipes to equilibrate the counterpressures. always a good thing to do. I reckon I dont' understand why neither BMW neither AUDI does it on their V8 engines. all good exhsust manufactures do it.

difference between std and sport AUDI exhaust are in middle and rear mufflers which their part number differ. whihc would mean they have opened up a little the sound.... frankly speking I've heard both and the difference is not worth it. far beter to take std and change with aftermarket.... It is different for a TTRS where the sport version is more differente that std. and I reckon a TTRS sport version is good as is in sound for exemple (I show you this example for you not to think I am pushing for a sale, but being objective about things)