sound proofing the car

Have anyone tried sound proofing their cars? I bought some sound absorbing foam, sound reflecting vinyl, and sound damping vinyl for my car. I put them under the front carpets (absorb + reflect) , inside the front doors (damping + absorb) , over the rear shocks/wheel well (absorb + reflect) , and my tailgate (all 3) (the inside of the tailgate was comptelely empty... made me wonder if I bought a Kia instead of a volvo). The results were pretty good, the exhaust noise was greatly reduced, also road noise is a bit lower, the wind doesn't seem to seep though the door much now... and I guess since the car is much quieter overall, I'm beginning to hear the transmission whine a bit more now. It is much quieter at higher speeds than before now, I almost don't need to turn the radio up at all no matter what speed I'm at. And I can floor it and not to be overwhelmed by the engine/exhaust (some of you won't like this!

Wanna hear from you all if you've done anything like this and the results