I am looking for any advice I can get. I have a 1993 Lexus LS400. My fiance was driving the car while I was at work, when he was backing out of his friend's driveway, he said it sounded like he hit something or ran something over, but when he got out to look all he seen was a rock. Now while driving down the road it makes a grinding noise that sounds like it is coming from underneath in middle. It sounded like it was coming from underneath the middle console, so while it was making the noise I felt the bottom of the middle console and felt a vibration. I have noticed that the car only makes the noise when we push the gas peddle, when we let off the gas the noise quits. We have checked the exhaust, as the car has a skid plate and we can not see anything else, it was not loose. We are planning on taking it to a shop on Monday, But we would greatly appreciate any advice or ideas on what it could be, so that we know if it is something we can fix or not.