A couple of months ago, I purchased an Intec Headset Adapter for my Xbox 360.  I really dislike the over-the-head form factor used by the official Xbox 360 headset, and really prefer the behind-the-head form factor of the original Xbox Communicator headset.  Unfortunately, the original Xbox headset doesn't have volume or mute controls, which is why I bought the adapter.  After a couple of months of usage the adapter had become loose when connected to the 360 controller.  The body of the adapter would wiggle when trying to adjust volume, change mute status, or even just plugging in a headset.  After taking it apart, I found the problem: the plug is not anchored to anything!  Knowing the problem, I resolved to fix the issue.  So, armed with a small Phillips screwdriver, a soldering iron, a Dremel rotary tool, and a spare Xbox 360 headset, I set out to fix the problem.

In the photo below, you can see the difference between the plug from the Intec adapter (on the left) and the Microsoft headset plug.  The Microsoft version has two prongs that fit over the screw posts and anchor the plug to the body of the dongle.  The Intec relied on a friction fit in the plug faceplate that is prone to wearing out.

Obviously the Microsoft unit will be more stable, being anchored by screws, so I decided to swap the two plugs.  First, take note where each wire goes.  The Intec unit has red, blue, and copper wires, going to SP+, M+, and G, respectively.  The Microsoft unit has black, blue, and copper wires going to the same connection points.  Carefully de-solder each plug from its circuit board, and then solder the Microsoft plug onto the correct connections on the Intec board.  This should be relatively simple to do, as you just need to melt the existing solder to remove or replace the leads.  No extra solder was necessary for me.  Make sure your solder joints are good, or you'll have to re-do this step later.  While you're at it, there's a little rubber wrapping at the base of the Microsoft plug that's going to get in the way later.  Slide that down the wires and out of the way so you can bend the wire connecting to the very end of the plug.  There's going to be very little clearance between the plug and the jack when you put this back together, and the rubber thing just gets in the way. 

Below is a picture of the SP+, M+, and G connection points.  This picture is after soldering on the Microsoft unit, so SP+ has the black wire at the top of the photo, M+ has the blue wire at the bottom of the photo (a little hard to see), and G has the copper wire in between the two.

Once everything is soldered, it's time to put the Intec unit back together.  Immediately you'll notice that the faceplate (the slightly curved bit where the jack sticks out) is different between the two units.  Not a problem.  Just grab the faceplate from the Microsoft headset and use that.  In the picture below, the Intec plate is on the left, while the Microsoft plate (as indicated by the "Microsoft" label) is on the right.

Now that the faceplate issue is sorted out, you'll find that the two halves of the Intec unit still don't fit together.  The top plate was not meant to work with the anchors from the Microsoft plug, so we're going to have to fix that.  Using your Dremel rotary tool, select an appropriate grinding bit for plastic.  I used a cone-shaped aluminum oxide bit (similar to this one) because that's what I happened to have available, but a sanding bit or otherwise abrasive bit should work just as well.  On the backplate, you need to grind down the screw posts, the little pointy bits next to the posts, and the two ledges at the front of the plate.  On the Microsoft plug, you'll want to grind down the upraised portion on the prongs that sit over the top of the screw posts.  I just eyeballed it, grinding and test-fitting as needed.  In the picture below, you can see the backplate after I finished grinding.

Once everything fits back together, insert the two screws and you're done!  At this point, you should fire up your Xbox 360, plug in your chosen headset, and record a voice message to a friend (no need to send it).  This will test mic functionality (recording) and earphone functionality (playing back the recorded message).  If all went well, you're truly done.  If the sound is scratchy or non-existent, try using the headset directly with the controller to see if it's a problem with your chosen headset or with the adapter.  If there is a problem with the adapter, you'll need to take everything apart again and re-solder your connections.

Now you have an Intec headset adapter that doesn't wiggle when adjusting controls, and doesn't look all ghetto like you'd get if you hacked your own adapter (I did that before Intec released their unit, cannibalizing an old Xbox headset puck for a jack; it worked well, but was quite ugly).  Enjoy!