I got it fixed with the power vision this weekend. Wasn't % based, it's a "pulses per kph" setting. Took some back and forth making adjustments, but I got it dialed in. Thanks for the answer.

 

The adjustment isn't in percentage, how you express the error to others should be.
5mph off at 50mph = 10%
At 100 mph the error will still be 10% but the speedo error will now be 10mph.
Likewise in the above example, if you simply adjusted your pulses per kph by 10% you would have the correction.