Got a JB4 with DCI. Runs great on 91 octane and map 1. Runs even better when I mix in half a tank of 100 octane (~95.5 octane mix) and run map 5.
I have been pretty satisfied with it but I keep throwing misfire codes. Pulled the JB4 and took it to the dealer. Spent the $50 deductible for them to tell me nothing was wrong and not really do anything. Drove it for three days without the JB4 and had no problems. Put the JB4 back and started throwing the same misfire Cyl1/Cyl4 codes again... Really annoying as once it misfires, it keep misfiring and you either have to clear the code (which means I can't save it to show the dealer) or stop the car and shut off the engine to get it to stop (hard to do on the freeway @ 80mph).
I decided to change the plugs myself yesterday since the dealer refused to do it (lucked out and got 5 new plugs from an ebay auction for $10 + #6 for $12.60). Don't think the dealer even pulled them. They are visibly worn with a larger gap (apparently CPO warranty and BMW Maintenance plan are about worthless if they won't even change plugs that show excessive wear after 15k miles). Will have drive it a few days to see if that fixes it.