Removing the air silencer in stock 87-93 5.0 Mustangs.
I just took out the air silencer in my '90 LX, and here is the article to show you how to do it too! This mod will get you 1-2 horsepower, and maybe 1 ft-lb of torque, all for $0, and about ten minutes of wrenching. Good deal, eh?
The first thing to do is pop your hood, and look inside:

Look to the passenger side. See the air intake? It looks like this:

We're gonna have some fun now.
Now, remove the plastic cover like so:

This exposes the air filter. Remove that as well:

This, in turn, exposes the back half of the stock airbox.
Nowt, get a handy-dandy 7/16ths inch socket, and wrench:

This is a 1/4 inch version, but a 3/8ths variant will work just as well.
Now, loosen and remove the 7/16in nuts that attach the back half of the airbox to the fenderwall:

See?

The nut with attached washer looks like this.
Now, take the back half out, like so:

After doing that, you can now see what you are going to remove:

The air silencer is on the other side of the fenderwall there. It is held on with three 7/16in nuts. Remove them:



The last one is a bit of a pain to get at. Move the wiring as best as you can.
The nuts with attached washers looks like this:

After removing the last (bottom) nut, the silencer falls out, and slides downward and forward for removal. It was a bit of a pain to remove it for me, but only took a minute or two.
What you have in your hands now is this:


Made in Canada. Hmph.
Anyways, what I did after this is, I took the nuts that held the silencer on to the car:

And threaded them back onto the silencer like so:

I then put the silencer in a safe place, in case I ever want to restore my Mustang back to the original factory specs 20 years down the road. I suggest you do the same. Or sell it to me!

Reassembly of the stock airbox and such is the opposite of disassembly. I suggest you take a good hard look at your air filter, and make an educated guess whether or not to replace it with a new one. Now would be a good time to do so, when the airbox is disassembled.