Fuel was fresh, tried a friends 20% no difference. Had the test mount mounted to side of my shop and when I went inside with the engine running. There was a gosh awful vibration - knocking sound inside the shop. My friend has a 150 and it idles and runs smooth, low vibration. Ticks over smoothly at idle, mine sound as thought the airframe is coming apart from the beating it is taking.
courious!!