a guy i work with bought a cheapassdieselchip.com pretty much 5 resistors with selection knob from what i have read.
Truck runs good in all settings great thottle response great low end power
but in the top 3 settings under heavy 3/4 thottle it shifts threw all gears fine but when shifting at i think 55-60 into 5th it starts to lurch or cut out maybe slipping it does keep pickin up speed

fuel filter has been serviced
any ideas to what this could be
any thing may be help full
thanks