93' 2.8L M104 motor - 225K miles.
When I accelerate I have noticed since late summer/fall what sounds like a small can of coins faintly rattling at certain throttle positions. This is during around-town driving. For example, accelerating from 25-30 with regular throttle increase, I hear the rattle. It's faint but seems to have gotten slightly louder over time. I can't hear it happen at any acceleration above 50 or higher.
I can't reproduce the sound by looking under the hood and revving the motor at different rpms. It's only apparent under load. I thought perhaps my damper/belt tensioner which were replaced about 4 years ago. But like I said, I can't get the sound to reproduce with the hood up. Could this be timing chain/tensioner lash?