While riding my slingshot through the mountains yesterday I noticed at low RPMs there was a vibration coming from under the hood. From the type of sound, I believe the noise is coming from extension spring vibration from the springs used on the exhaust. Has anyone figured out how to stop this noise? Normal RPMs the noise is not there, just at low RPM when ready to down shift. I've looked for something to put on the spring hooks to function as an isolators, but no luck so far. Thanks.