I removed the plastic clam shell that covers the steering column today. It reduced my interior rattles by at least 50%. After getting a taste of silence I can't go back. Here are the options I'm considering.

(1) coat the interior with felt tape and cover the adjoining edges with tar.
(2) replace it with an aftermarket boot-the type that is used in conjunction with aftermarket wheels.
(3) leave it bare and try to refinish the plastic/metal parts to blend in with the dash better.

 

This is a common rattle to most FDs. I used a small & thin rubber washer between the plastic clamshell mounting holes and the mount itself (where the screws go through). Absolutely no more rattles!! Give it a go you'll be amazed at how this works....I am assuming that your clamshell is still in reasonable to good cond.

 

mmmm, clams....

Anyways, mine rattled a bit after I took it off a few times when removing my gauge hood to fix the tach. Turns out it just wasn't lined up right when I put it back on.

Try taking yours off and putting it back on, making sure that everything lines up correctly. Worked for me.