Todd, I think our Aeroforce gauges are pretty accurate. With 4+, I had a 1/4 speed of 104. With the 4X+, at the track, I had 107.4 - a 3 MPH improvement. The Aeroforce gauge did have my ET at 12.74 but I did that run at 3 AM on a very cool April morning - ideal conditions.
If I adjust my track time for the density altitude at the Brainerd track, I would be at 12.5 @ 109. Altitude, humidity, temp and barometric pressure play a huge role when you are trying to shave off tenths of a second!
At the end of the day, all I really care about is great street performance - and we both have that!