Any have any experiance with losing performance by going mid-pipe st8 to muffler.

off road Xpipe to Borla XS, and turndowns to keep the heat off my dif

 

im not exactly sure what it is you are asking... but you should run a cross-over mid pipe, like an H pipe or an X pipe. As far as mufflers... its whatever flavor you prefer. keep in mind that dumping the exhaust under the car can cause alot of interior noise, and will allow for the collection of fumes under, and inside the car