I was putting my EFII XR6 instrument cluster in diagnostics mode and I pushed the wrong sequence.
Up pops a speedo adjustment from -16 to + 15.5.
This actually changed what my speedo read up and down.
I am not sure if this is in percentage or actual amount but it works.
I now have both, diagnostics mode,
(Hold trip button in for 10 seconds etc)and for the speedo mode I just turn on the ignition and hold the trip button in for 5 seconds and up pops the speedo adjustment.
I thought the police dash was the only one with speedo adjustment?
So if anyone else has a XR instument cluster try it and see if you get the same results.