Get the high boost. I know from experience to not start with the low boost one. Also if it is calibrated correctly it's dead nuts. Mine matches my boost gage perfectly.
The Boost Overlay can be ordered at Hilton Boost Overlay they are $29.95 and come with complete installation and calibration instructions. If you have any install questions just call our highly trained and fully staffed engineering and development department. Well, actually that would be just me. LOL. I'm always here to help you with any questions.
Thanks for the interest.
Ray H.