+1 on DynaMat that stuff is good, except if you were to ever remove it, it would be quite a task.
Also, the headliner is pretty simple to remove except for a certain part.
The shortened version:
1. Basically remove all the trim pieces on the side of the A, B and rear pillars that are around the headliner.
2. Then, carefully remove the plastic tabs holding the headliner in.
3. Remove the center unit that includes the "bluetooth" microphone, if equipped, and dome light. These are incredibly easy to remove, as they are just pushed into place via tabs.
4. At this point, the headliner should be slouching and only held in by the sun visor region.
5. Go ahead and remove the sun visors and their brackets.
6. Finally, and this is probably the hardest part I had, remove the little retaining plastic piece that holds the sun visor to the roof of the car. This plastic piece is extremely difficult to remove as it is "popped" into place. However, with some side to side prodding, you can remove it without damaging the piece (or you can just snap it off and go to the dealer I suppose).
7. At this point, the headliner should be free. All you need to do is apply the DynaMat, let it set, and reinstall in reverse.
Enjoy!
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View my fuel log 2014 Mirage ES 1.2 manual: 45.8 mpg (US) ... 19.5 km/L ... 5.1 L/100 km ... 55.0 mpg (Imp)