This is a very interesting problem started a week ago the a noise that sounded like it was behind the engine at the firewall started. The noise started out as a mild clacking whacking noise that got louder as engine rpms increased.I turned the engine off and started her back up the noise was gone for a while then came back . Car sat for two days drove her agine no noise. Took her out again was fine for the trip to the mall however on the way back the noise started again at start up . I killed the engine it went away again. Now the killer while driving at 40mph on the highway in fourth gear(brand new t5z and king cobra clutch about 500miles) a horrific whacking clacking noise started. The noise was so frigin loud i had to shout to talk to my daughter right next to me . Put in perspective i estimate that someone living a half mile away could have heard the whacking clacking noise . the car also popped out of gearthen i pulled over to check the following I checked oil presure was good at 60 psi on auto meter gauge air fuel ok per wideband o2, and timing i checked on the timing computer in my glovebox ok at 14 base. I pulled over and checked the oil level it was fineand fan shroud ok to . The noise has not stopped and is super super loud. Louder than the offroad exhuast with my gt40 e303 crate motor with only 40,000 miles on itand powerdyne which was off at the time.. The tech at the auto place said by just hearing the car idle that it has thrown a rod I thought when a rod goes it lands in the oil pan or goes through the head. Let me know if this sounds like it could be a thrown rod Personaly I thought maybe the flywheel came lose or the clutch ripped but the car still is able to move. Any advice or help would be appreciated .Sounds like holding a wooden ruler against plastic fan blades whack whack .