Yes you can but its all in your clutch work , that's why your cars jumping. You don't have to change the gas at all. Drag cars don't let off the gas to shift when downshifting, naturally your car wants to stay at the speed that it would be at that many rpm's. so when downshifting you do not let off the gas at all unless trying to stop. So, when racing at interstate speeds and you want to downshift put the gas to the floor, and then press the clutch to shift and the rpms will spike up, shift, then release the clutch. Don't take your foot off the gas when drag racing. the only jump you'll get is a fast forward one. and practice before you try racing. Good Luck and have fun