I would avoid the dyna boxes. Man I had horrible issues with mine and finally just chucked it in the trash. I didn't want to sell it to anyone and have them come attack me when it started doing what it does.. Which is randomly cut out completely.
Mine had been sent back to dyna 2x and both times they said they repaired it and it was perfect. It never was. Would run good for about 30 minutes, then it would start.. Going downhill for long period of time (like forest roads) I would push the pedal and get nothing, had to hit it like 10 times to get the motor to kick back in.. Going up hill it would randomly die out, and I would have to pedal to get it to come back to life.
TPS Tested perfect. All connections were checked, and it just wasn't ever right. MSD is perfect.