New toy :)
 

Hi .... Just acquire a beautiful yellow 2.7. Love it to bits but serious back end rattle going on. Any ideas ? ?

Congrats on the car. Pictures are required.

You are going to need to provide more details about the serious back end rattle to get any helpful response. Based on your description it could be as bad as the car's motor ready to implode.

Or as simple as worn out stabilizer bar bushings.

My best guess is somewhere in between:
http://986forum.com/forums/diy-project-guides/60057-rear-trailing-arms-replacement-guide-diy.html

The heat shields are notorious for rattling if it sounds tinny and not a deep clunk type of rattle.

Get the back end up off the ground and get under the car with a poking device of some sort and start tapping and poking around.

I replaced the rear trailing arms this past weekend. Easy job!