I have a 2001 Ford Mustang 3.8L V6. The previous owner had taken the throttle body off and had installed a cool air intake. I got on it about a week ago and when I parked the car it sounded like there was a rod knocking. I started it two days later and the sound is actually coming from the valve cover on the driver side back toward the firewall. I am guessing either a bent or broke valve. I am also guessing the previous owner was trying to modify the car for racing and had probably red lined the rpms a lot as the car has only 151,000 miles on it. Any ideas?