Mustang GT speedo problems

[johntimber]

Hi,

I have a 2000 Mustang GT 5sp and a U7146 Predator tuner. I bought it to change the 02 sensor configurations and the speedometer. Ok so heres the deal. When i instal the diablo tune, my speedometer is correct when it's set to 3.73. Now that i have nitrous, i set it back to FACTORY HORSEPOWER TUNE and set all the perameter to the way they were before. Now my speedo is a perfect 10mph to fast. I tried reinstalling the back up tune and starting over, i have tried reinstalling the diablo tune and taking out 8* of timing to get my desired 16* but the car is getting way to much fuel with the Diablo tune in. Can anyone tell me why the factory horsepower tune will NOT change my speedometer no matter what gear ratio i set it on... but it will under diablo tune....

Please help.

I didn't find the right solution from the Internet.

References:-
https://forum.diablosport.com//viewtopic.php?f=9&t=3699" onclick="window.open(this.href);return false;
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Thanks!