have started to notice a rattling noise upon acceleration from dead stop but only when engine is hot and only upon initial acceleration (as in leaving a fast food drive through window). don't hear it when just revving the engine. wondering if it could be catalytic converter. car is 2000 model with 95K miles

Would a better description of this noise be; it sounds like someone shaking a can with BB's in it?

not the typical catalytic converter bb's in a can sound. more like metal flashing vibrating against other metal. thanks for any advice

Have you checked the heat shield above the cat, and how about the harmonic balancer? The balancer usually makes a hammering sound, may not be the case here! Have you ever had any type of transaxle service?

There may be a heat shield above the muffler too. I see one edge of mine is rusted off.