interresting.. so maybe bumping up the nitrus wont have any effect like that...
the only difference between tank and car engines and airplane/missile engines is that the tank/car engines provide their power through spring objects, and the airplane/missile engines apply thier power directly to the universe. maybe the third party (the springs) is whats jerkin things around.
maybe it would be better to instead of bumping up the tank/car engines, to instead just "glue" on a missile engine with things toned way down to the vehicles, and with the setInputToRoll set to the thrust button (dunno what it is off the top of my head.. u know, the "w" key). you'll hafto try it out and make sure that when you jump a dune with a tank, you don't catch
too much air