2012 BMW 750li misfire (help)

[Tmankiller15]

I recently purchased a 2012 bmw 750li and I drove it back from New Jersey, I didn't know that it was premium only gas dud about 2 tanks of mid grade on the way back the rest of the fill ups were premium. I got it home after 2,100 miles and found out it had a misfire, replaced sparkplugs the best I could buy and factory oem bosh coil pack and was running fine for a day or two, then the misfire came back. Any ideas on if my fuel Injector are just plugged up or if it somthing else. I have a BMW software to Diagnose the car but don't k ow gow to use it fully. The car sat with a dead battery for a week and had to be jumped. Afterwards had 56 fault codes. Normal??

On another note I had some subs hooked up, they were tied into the postive battery distribution block, guess the installer didn't fully crimp the terminal, and the amp cord ended up shorting out on the frame. Now there are a bunch of overvoltage codes and unndervoltage codes as well. Would that just be a new distribution block I need to order or did I fry some electronics. I check all the files in the trunk and behind the glove box. No blown fuses.