Does anyone know what brand the stock muffler on a 91 jeep wrangler S 2.5? It doesn't have a catback but instead has a turndown. It has a huge hole in the top of the muffler. The reason I ask is I am hoping it is a Borla because of the million mile warranty they have on their parts. THe reason i say stock is the muffler looks like it is atleast 15 years old because of rust,etc..