I know you unplugged it and said it was fine, but did you try putting the stock bulb back in too? If it still has rough idle with stock bulb, then my guess is alternator or regulator, but that's unlikely since it was running fine before the swap.
Also, did you check if it's grounded correctly? (Not sure about the 919, but sometimes low beam is a lower voltage than high beam, thus, there would still be a potential difference b/w the two leads, so if the two leads are connected in the right(wrong) order, the LED might still run, but would probably cause issues with ECU).
Like Badmoon said, those specs for the LED driver are all over the place. It could very well be a load issue if the driver is faulty and not blowing the fuse for some reason. Could also be a feedback issue
Not an expert, but here are some tips:
Check battery voltage difference b/w stock bulb and LED (with the bike running)
Check your Grounds
Check the current draw of the LED
Check alternator and regulator