Hi, I have a Mazda 3 with a 2.5 liter motor with 125k miles on it, recently, I have been hearing a clatter noise coming from the engine bay. When I start the engine in the morning, after warm-up, I take off and hear a clatter noise between 1500-2000 rpm(between 20-30mph). After 30mph the noise goes away. The noise comes back when I'm at a steady 30 mph or 1500-2000rpm. Any ideas on what is causing this noise? Could it be the intake manifold flaps inside? Could it be the timing tensior? Your help would be appreciated.

 

A vid with sound would be helpful. Could it be a gasket? 125k isn't a crazy ton of miles but definitely enough to possibly eat an exhaust gasket. Maybe check that gasket between the exhaust mani and the down J pipe.