Eliminating the cats will get you in trouble; maybe not now, but when you go to sell or trade in the car. Its illegal to sell or trade a car without the cats. Either a provate individual that you sold it to can come back after you and force you (by law) to either take back the car at full price (even if you sold it "as is"), or a dealer can retract a deal made. Both of these can also net you a 30K fine by Federal law, regardless of local laws.
As to if it nets you any additional performance, I doubt any significant gains to make it worth removing them. If you have a V6, the 5.0's will require some end tube modification, as the 3.7 V6's exhaust is smaller in diameter than the late model 5.0's.
It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt.