Not uncommon at all on these things. Our '04. 5 had the pipe rust through in that spot in a little over 3 years. I replaced it, as well as the one on my '07, with a good quality 304 stainless system. In fact, I think there is a MBRP on the '04. 5 and a Silverline on the '07. If you are going to keep your truck for any length of time, I highly recommend spending the money on a good system now so you don't have to worry about it again.