My '09 S is making a vibrating/grinding noise when I accelerate. When looking at top of the engine from the front of the car, all the way to the left of the cylinders in the block is a long rectangular section (lengthwise is front-back). its part of the one-piece case cover and just forward of the air box. What is this/whats inside? Something in there is pretty clearly hitting something else. Thanks for the help!