So after the install of my headers/poly motor mounts, I have a pretty significant vibration from about 11-1400 rpms. After the motor is warmed up, the mounts seem to soften a little bit and ease the vibration but it's still pretty noticeable. I'm sure it doesn't help that I also have poly rack bushings which transmits vibration from the K Member through to the steering wheel also. So my question is this: Without removing the poly mounts how can I ease this vibration? Will it reduce over time? Will a quality harmonic balancer help?