My custom exhaust

[Tonavi]

I had a custom exhaust built last Friday, with dual tips in the center. It was built from the axle back. (pictures are coming as soon as I can get a camera) I drove around and the car sounds GREAT on the outside, not too loud, raspy, etc, but on the inside of the car, there is an agonizing drone at all speeds. I went back to the shop and they said putting in a glass pack in the midpipe would solve the problem, but I was skeptical. An 18 inch one did nothing. Then we tried a 24 inch one. The vibrations are gone but the car is still so F&*@ing inside I can't stand it. Is there anything I can do to quiet it down, without investing too much more money? I'm in almost $500 and wished I never touched it to begin with. It almost makes me want a different car.

I thought of sound insulation, but would probably need so much of it I'd be better off buying the OE setup.

Any help would be appreciated.