A while back I started to hear a noise coming from the rear of the motor. It kind of sounds like a playing card flapping on bicycle spokes. Not much vibration though. At first it was only at start-up when I would rev the engine. It would then slowly fade away. Now I'm hearing it more frequently. I hear it wheather I'm in motion or stopped. Any ideas?

 

Exhaust leak at the head

Loose, or even missing, exhaust manifold bolts

 

Thats where I'm going to start. I put in a set of exhaust manifold gaskets a couple of years ago. Probably time to check the bolts.

 

There's why you have a leak.

Take those out of there.

Use a Roloc pad to clean the manifold surface, and a flat file GENTLY to dress it flat, and to dress the head surface; and put it back together with no gasket, like the factory did. End of problem.