Flowmaster installed backwards.

I was under my car today and noticed that one of my mufflers is installed backwards. One says inlet on the front and the other says it on the back. I just had this exhaust welded up about a month ago. Anyways, my question is do I need to go back and get it fixed? Or is it even going to effect my power? I've heard of people running their mufflers backwards before. What do you guys think, should I make a big deal about it or not even bother?