Refer to guys like Roy Jones or even Wladimir Klitschko, most of their weight training consists of functional training/fast twitch development, not bodybuilding type training. I've personally witnessed top rated MMA guys get in the boxing ring to spar with boxers, in order to improve their technique, and the guys they spar with are half their size/age (mostly kids training for states/Olympics), and let's just say it isn't pretty.
MMA athletes are horrid from a boxers perspective in terms of their technique. They throw wide looping punches, that you can see coming 4 miles away. The kids they sparred with landed on them about 10-1 just to put it into perspective. Work on your legs and functional core training. MMA requires upper body strength for grappling, but in terms of enhancing speed, it's a catch 22.