its not going to be noticably different from standard, you may notice you use an extra half of a cent every tank. the inlet manifold doesnt have a hole in it if your worried about that it just has a heat sink.

the setup with the 2 inch straight through will sound fine but dont buy a crappy brand muffler. go with something that has been used before. i have tried a few and recommend lukey, mercury one that starts with b cant quite remember but it was defientely the best. dont get superkat as they a a real tinny sound.