2015 isx15 565hp

[Dj3608]

Need help with mileage , engine gets poor mileage have followed rawze instruction cleaned/ replaced sensors. Minimal gain in mpg 5.2 or worse loaded depending on wind/weight. Need advise on mileage improvement, heard from drivers getting 7-9 mpg with these eng- by tuning ( opening up parameters on ecm )with all factory components still active , how is this possible with egr choking the engine down I am in Oklahoma and need assistance please ,,tired of pumping out cash through the pipes