I recently bought an ST170 and keep reading about there being hoplessly down on power. Mine seems quick enough but im not sure if i have an issue with my VVT. It does not seem to kick in till 6250+rpm when it should be at about 5000rpm, what gives me this impression is when at WOT approaching 6250rpm you can hear a distinct engines note change which im guessing is the vvt, you can hear the standard induction noise then at 6250rpm+ it almost goes quiet as the engine noise changes completely. Is this right and is my VVT kicking in too late, can this be rectified?