years ago I went to get a '82 GT inspected which had LT's and no cats. As soon as I pulled in they looked for cats. They told me as soon as they heard it they knew something was up and they would'nt inspect it.
What I did was pack my tailpipes with steel wool and drilled 2 small holes in each tailpipe and ran a peice of wire across to hold in steel wool. Which made it alot quieter.The next day I went to another inspection station and they did'nt even notice.After I went down the street pulled over to undue the wires holding the steel wool and then got on it blowing the steel wool out the tailpipes.
If you did something like that you should'nt have any problems if your cars passes the OBDII.

 

The steel wool is a good approach, and relatively cheap. I added a Car Chemistry header muffler to my exhaust system and it didn't do much to muffle the sound. At $60.00 a unit, it isn't cost effective and it required a lot of test fitting to install in my case. Ultimately, I used a personal connection to get a sticker. I would have tried the steel wool if I had no other options.