106 will not get you low 12s without an extremely light car or a miracle... My car runs good numbers for the low mph and doubt it will ever clip a low 12 with that mph. Not to mention a Gtech measures mph at the exact 1/4 mark, and the track measures it over the last 60' of the track. The Gtech will be a mph or two high on average from what friends of mine have seen.
Also without real track numbers its hard to say. Spinning tires will throw the Gtech off and especially if your on a bad road. Id say dont worry much about these numbers until you get to a real track. Use a Gtech to see what a new mod will do on the same road and such, but I wouldnt use it to judge how fast a car is compared to another!