[Biggy118]

So I just bought a 2015 335xi GT. Most of the posts I am seeing say this car should have 300HP. My Sport Display shows 320HP and 320ftlb of torque. I have not MPPK or otherwise... I am wondering a few things from the experts here.
1) Am I just wrong? Why is my car showing 320HP when most people are saying 300HP without the upgrades?
2) If I did get the MPPK on this car, what would be my HP and Torque ratings?
3) Are there any MPE available for a GT? If not, what exhaust would be the largest increase for my $$.
4) What other performance upgrades would people suggest?

Really confused on the 320HP vs. what I read everywhere...