Nort,
I think I saw a picture of you airing out the 382 bigtime on the SCOPE website. Isn't the accuracy of the GPS affected by the vertical trajectory of the object in motion relative to the horizontal distance travelled in relation to the motion of the multiple satellites orbiting about a moving sphere? No wonder your GPS is off by 3 mph! Is that running with or against the current?
Did you start with unlabbed 28's and if so, who labbed them and what changes in speed/rpm did you see after labbing?
Are you spinning them in or out?