Also had the constant rebooting/black screen problem on my f90bt version 3.01...but thanks to this thread the problem is alleviated.
Props to funk101 for providing the key to actually getting into testmode.
My fix process:
1. Put testmode (ver. 2.3 for me because firmware is 3.01) and mitacap folders onto SD card. Insert into Avic.
2. Turn ignition on. Hold down eject and reset buttons. Release reset after a few seconds followed by eject in a few more seconds. Give the unit a bit to boot into test mode.
3. Go to my flashdisk, highlight gpspara0, gpspara1, gpspara2, and gpspara3. Go to