There is rattling noise and some vibration only when im driving and let go the gas pedal...

Hello, Without hearing the noise first hand I think of two things. First is motor mounts. When you let off of the gas pedal, the engine acts as a brake, so it wants to tilt in the opposite direction as when you are pressing the gas pedal. If there is excessive wear in the mounts, this will give it room to move/rattle/vibrate. You would also notice slight vibration while sitting with the engine running in park. Second, I think of the exhaust system. If you have a worn or broken mount or heat shield, the engine shifting when you remove your foot from the gas pedal could cause contact between tin and steel components. Vibration would not be so so pronounced.