a customer tune cant be made for off road use??

u7186
9R08
07 lbz 2500 dmax classic crew cab 4x4

1st question: I need a customer tune please, i installed the egr delete plate and its throwing a code p401. I use the 85 tune

2nd question: Is updating the best thing to do in general? If yes then I would prefer the custom tune to be set for the ...

ok i have a 04 1500 5.3 with a 4" rancho and a 3" body lift on toyo open country MT 37x13.50R22 i have played with the tires size and still cannot get the speedometer to meet the gps i lowed the size from 343x55r22 and when i hit 70 its 77 on gps. once i hit 50 thats when the descrepency starts it ...

i have a 04 chevy silverado 5.3 with a 4" suspension lift and a 3" body lift and i have 37 inch tires and 22" rims and my speed is off by like 5 at 40 and 70 its around 7 to 8 i change the tire size in the programer to 343 metric i looked up the conversion online and im wondering if theres any way ...