My car also rattles. It drives me insane. I always assumed it was just the resonator but it was a lot more than that.
But I also had a clogged exaust so I went to extremes on mine. I had the precats removed and replaced with straight pipes, the main cat replaced with a high flow one (this was clogged) the resonator cut out and replaced with a straight pipe.
And now it turns out my muffler is RATTLING!
So that will be replaced soon too!
Time for a trip to Jegs.