Again, you will not experience any significant power increase without an engine retune. You cannot just add a 3" exhaust and expect your ECU to automatically increase the boost just because of a decrease in back pressure. Your ECU is not just going to say, "hey, I sense an extra .5" in diameter and 2.16 in^2 of cross-sectional area so let me run some more boost, increase the A/F ratio, and advance valve timing so we can get more power." It requires a reflash. This is the same reason why running an aftermarket DP will not yield any significant gains unless you reflash.