All analogs read slow. Ours will read pretty much like the next guy. I've run up to ..... not gonna say how fast, but my GPS is VERY close to the VSS reading on the scantool and the HUD. VERY close. Some people see a larger error in the HUD to analog, but that'* normal. Mechanical device. Accept it. 2mph is pretty mild.
Let me also say that at certain speeds, it'* very nerve-wracking to try to watch the scantool or GPS. I have a hard enough time looking at the analog speedo needle buried in the column.
I figure if Turtle and I both went WOT on I-5 at the same time, we'd pass each other in about 2 hours
(at a head-on impact speed of XXX mph!)