It's not that big of a difference in diameter so you won't have any issues. No you won't have a leak unless you don't tighten the bolts properly or have a busted gasket which won't happen unless you break something on install. No you won't have an issue if you get the Nameless FP/DP. If you're looking for a FP/DP Nameless is the one I would get, and already have. For exhaust I'd get Perrin, Nameless, or Invidia Q300 if you don't want to wake the neighbors every morning. Worry not my fellow enthusiast and enjoy your car's exhaust.
