I have a 3500 4x4 six speed single rear wheel, smarty 67me, turbo back 5 inch, egr delete, and was getting about 13 at 70 mph, after i took off all of the junk, deleted, run the smarty on lowest setting due to clutch slippinglol, i get 19 to 20 on the overhead at 70 or 80 makes no difference...