i had a xpipe installed a few weeks ago and i've been noticing on startup a rattle coming from my catback on the drivers side. so on further examination today i noticed that the drivers side pipe is crooked and the pipe is touching my gas tank cover, which has melted a nice hole into it. i would assume this is bad.
Try turning it where the cat-back and mid-pipe meet and it should take it off the gas tank. It did on mine... 
