ok for this p1000 code it says to drive for 10 minutes at different speeds, but my problem is i glashed my pcm back to stock so how can i tell for instance what 25 mph is with 33s on the truck . I know there is a tires size calculator , anyone know where it is.

 

This will help... http://www.1010tires.com/TireSizeCalculator.asp

 

its not that far off.