NU3001 ia 4.4.2 unfortunately.. there is a guy on XDa working on porting 6.0 to it, he tried 7 but found a dead end stopping him from that.
Currently on my bench I have my Nu3001, the MJS USB cable and the HDTuner, working well. I find if I use a separate switch to turn the HDTuner on and off, I get better connectivity/ repeat-ability. I suggest if the HDTuner is ‘on’ in software prior to turning off the car, then On a restart if android was asleep, assume the radio is off..
I will reply to the HDTuner thread for the other stuff