Where is the carpet getting wet? In the front or rear of the Limo?
Couple things you may want to have checked...
Validate all the drain plugs are properly placed on the underbody of your Limo.
On my 98 Town car, I had a very similar problem in the front of the car and I had to seal several cavities in the engine compartment. i.e. where ever there was a cable entering into the car, I sealed and this corrected my problem.
Hope this helps... Good Luck!