Is there anyway to increase the engine power of the S40 or anything I can add to make it more stable in the freeway? I have no trouble on highways up to 55 -60mph. around 65-70 mph which is the speed limit in most freeways, I find that it vibrates and feel it struggling. It is pretty rough esp in windy days. I´m 5´1 and under 110 lbs so that probably doesn´t help ...