Go get the car weighed instead of using worthless guesstimated weight data.
Though it's not like the data you are going to get from the G-tech is going to be very accurate unless you use a strict testing regime.
Flat ground, multiple passes both ways average the info, using 3rd gear (drag hurts numbers in 4th and 1st & 2nd are far too short to be accurate), et cetera...
It's a fun tool for comparing changes once you have an accurate baseline. ACCURATE being the KEY word.
It is 100% WORTHLESS for comparing against anything else. PERIOD!