When you are floating in the air while jumping via the big jump, steer to the left. This will give you some effort. Don't steer to much, or you will end up swimming. When you are driving in the cave, just drive straight ahead, while avoiding the last most steep piece of road. This piece of road you will only make with a turbo. Some pieces you can shortcut through the grass, but use the turbo for this, because the grass will slow you down ofcourse.