Take a 4 foot section of old water hose and use it to scope out variou areas of the engine. Put one end to your ear and take the other end and run slowly all over and around the engine. Believe me when you get to the area of noise you can noticeably tell the difference. I found the problem with a new car like this once. The dealer was unable to find the noise after repeated trips to his service facility. While changing the oil one day I picked up a clean piece of water hose laying on the ground and used this method. Within 5 minutes I found the leaky exhaust tic and took it back to the dealer and instructed him to repair.