If you mean ECU Unleashed instead of ECM I can tell you that I would not willingly give them any of my money... I don't even have experience with Guhl, but I would just about try anything rather than dealing with ECU Unleashed
My experience as outlined here
ROGUE RACING Gen ZX-10R ECU Flashing
My experience as outlined here
ROGUE RACING Gen ZX-10R ECU Flashing