I bought my 2005 FX4 used with 55k miles on it. It now has 136k. When i bought it the previous owner had installed a dual (not true dual) exhaust kit on it. The tips at least were Magnaflow, not sure about the rest. I have had continual issues with the exhaust from the muffler back rusting. I have had each exhaust pipe rust off right past the muffler twice on each side, and now its happening again. I could understand this maybe if I lived in Michigan and had all the salt, but I live in TN, and the original owner also lived in TN. What is the deal here? What could be causing the exhaust to rust this bad that it falls off over and over? I just wonder if whoever installed the dual exhaust bought the cheapest quality metal imaginable or if its something i may have done/am doing. I keep the truck clean though, it gets washed at least a couple times a month, and i've never had it mudding or anything like that.

 

Must be poor quality metal. Save some $ for a stainless system and your problems will be solved

 

^^^This. Your exhaust is constantly exposed to water. There is a surprising amount of water as a product of gasoline combustion. Low quality metals result in exhaust systems that rust from the inside out. Get a high quality stainless system.