More info is needed. Do you have the 2.4 or the 1.4T? If you have a turbo you can delete the muffler. Cheap!
It's not exhaust, but I purchased the K&N intake off eBay for $80 very slightly used and it gives the Renegade a nice tone, but can get a little loud under heavy acceleration. I haven't really noticed any change in hp or mpg.