My Volvo "specialist" just changed the front pipe and resonator on my '82DL (B21A) - there was a hole in the front. From the first time I turned the engine on after the repairs, a very obvious rumble/noise started to come from the back - most noticeable from INSIDE the car. The entire exhaust is mint now and the car has only been summer driven for 4 years. They told me they will have a "specialist" from the older Volvo series have a look at it next week, but I am losing faith in them. Does anyone know why changing the front pipe/resonator would cause a loud noise from the back of the car? (mostly from the inside of the cabin). It's a rumble with occasional rattles. I looked at the back and there are no holes and it's relatively silent from the outside/underneath the car. Maybe they just gave me a really cheap resonator.

Thanks!