In the 04 STI it made a good difference doing the doors (a door kit did all 4 with some leftover), but the 05 STI really is already much quieter as is (and I'd assume the 06 even quieter the way Subaru is going with it). It did make a good difference in the 04 STI, but in the 05, the noisiest thing about the car were the tires/road noise more then anything. Changing those makes a world of difference. I've also read doing the back seat/trunk will help as well.06WRX said:would a Bulk Pack of the Dynamat Extreme be enough to do the 4 doors and trunk lid? Also, from those who have Dynamat, how much of a difference does it make and is it worth it?