Had a 2003 Hyundai Sonata worked on by a ''shade tree mechanic''. Had timing belt replaced and the valve cover gasket. Now it's like a log truck. It has a loud roar and a bad vibration. It has a high idle when first cranked then idles down (but still roars). It stops the noise and vibration when shifted to neutral (from gear in motion). Any idea on what this might be? Thank you!