So I just swapped my 2012 3.8 grand touring 3.727 ratio open diff for a 4.181 open diff. And can I say.... damnnn! Some very noticeable gains. Still don't have tires that can with stand the power, that's coming next week or so. All in all, I'm very pleased with what I have now. I have no other performance mods at all besides a muffler delete and I've already beat a few Mustangs and other performance cars. Lost some too, but sometimes you win, sometimes you realize you need more power(or a lamborghini, go with the lamborghini). On a side note, if I weld my diff, is it similar to an LSD?