Almost anything is possible. You can test the cat fairly easily. Here is a well documented case of how this is done.

http://www.turbododge.com/forums/f4/f15/499546-how-test-clogged-catalytic-converter.html

You can go straight to the process in post #20, or read the entire posting to get the history and deeper understanding of what and why. Hope this helps.

 

Its a sep problem,Tell in more detail when you get the vibration,accell-decell-cruise,in neutral reving engine at a stop?

 

At idle. It rattles the glass in the t top its so bad. Seems like I have some while going down road too, but tires aren't the best in the world, so kinda blamed them.Thanks Mike

 

Terrible rattle could be worn engine mounts too. They really should be looked at every time you do an oil change.