I used foil-faced foam from Homo-Depot (normally used under vinyl siding on your house); about 1/4 inch thick on the roof, and 1 inch thick on the roof sides. Excellent thermal as well as noise insulation, but a soft interior surface will absorb more sound than what is behind it. I have a 3/4 inch rubber mat on the floor and on top of the wheel wells in the rear of the 110. This also deadens a lot of noise from below.
For road noise, usually the tires are the culprit, and not a whole lot can be done about it (except getting less aggressive tread).
Under hood insulation is great for engine noise (particularly a diesel) but also the new one-piece foot well inserts are better than the older ones by far. I also run thick rubber mats under the factory (thin) rubber mats on the floor in front.
Also, the rubber cover for the metal rocker cover on the 300Tdi deadens a lot of racket from the engine... This might fit a NA diesel as well as a 200Tdi as wel- I've never tried it, but it may work.
Owner: James Leach Global Expedition Services.
1995 110 Regular