rattling noise
 

Hi there,

Between 1000 and 2000 rpm I hear a rattling noise, which is coming from behind the right rear seat. It's some kind of resonance. When I rev it up it disappears. I've looked at everything at the back seats but can't find anything loose.
I can't hear it in the motor compartment. Does it hear familiar to someone?

PS. It's a carrera coupe 1985.

Thanks,

-Kees. SmileWavy I've tried