I actually ran a full weight F10 M5 stock in my RB turbo car at 19 psi tapering to 17.5 in Mexico, the results were somewhat similar to the OP, but I put a half car on him early and held it til we cut off around 140. Keep in mind, the M5 is a boat, they won't trap well in the quarter mile because of all that weight, but once they get moving, that power starts taking over. I bet the M5 would have put some distance on me if we kept on going. Top end those things shine.
E90 LCI N54 6AT