True. 10% variation is a lot (145 vs 160). My speedo reads 4% less than actual (based on 5km road markers). Just pointing out that GPS aren't as accurate as some might assume. If you're going down a moderate hill they could be out by 5% or even 10% on a steep hill.

Cheers, Richard
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09 America, Staintune Pipes, K&N, Breathe, Hagon Nitros, AI & O2 removed, tune 20184 (modified), MTX-L a/f gauge