I have a verry strange rattle in my xr4i. It has the stock 2.8 cologne engine.
It occures on and off throttle around 3000rpm. They oil is changed 600km ago. Valve clearences are checked. Compresion good too. Ignition works fine too.

I also listnend with a stethoscope and it made the most noise arond the top plenum.

What could this be?