uninstalled cowl and cleaned shop. Made another attempt at updating G3X's but still no good. Performed nose high fuel flow test. Raised nose a high as possible (till the tail touched ground) to get a deck angle of 16 degrees. With 2 gallons of fuel in each tank I ran the fuel pump till it quit pumping. 46 gph on the left side, 41 gph on the right. drained 257 grams total unusable fuel, left and right combined. Thats about 1.5 cups of gasoline. Talked with Garmin support again and we determined that I was mis-registered with them and was downloading the wrong data set (G3X vs. G3X Touch). They made some changes on their end, I re-downloaded the data, and back to the airport I went. Sucessfully updated both screens, but it took a couple of hours.