I have a lg4. I have a carsound 3 inch cat and a pacesetter 3 inch catback system. I'm saving money for the 2055's. Can I use a tubing adapter with a 2 inch outlet and 3 inch inlet. Is this the correct size. Will it be hard to undo?

 

2-1/4" -> 3" would be better.

Install the cat & cat-back where they belong. If you then cut the existing y-pipe, put the adapter in and clamp the adapter to the cat inlet, it won't be too hard to remove when you get the proper headers & y-pipe.