Ok with this secret you could get more air and stuff: before jumping off a ramp, press x down and let got off x at the right time before jumping off a ramp... you could get rank x jumps on metal city on that first ramp after the finish/ starting line... and on the final ramp before the finish line ( the one that gets you to the building where you rotate the joystck to earn fuel) there are some other places but those jumps wont get you to rank x only to SS or 55 mostly