I stopped the pi, disconnect GPSBerry, put a wire loopback between Tx and Rx
Started pi, do minicom -b 9600 -o -D /dev/serial0
No i don't see extra characters in minicom
Yes, when i typed within minicom, i can see the characters i typed.
please find also a close up photo here of the header and gps part of the BerryGPS-IMU.