you can usea cat-back system but you will have to take it to a shop so they can add extensions between the cat pipes and the cat-back system, i am told. also, the driveshaft would be better off made from scratch. z1motorsports sells them at a fair price.
i am going to be working on a 2+2 TT swap and i have done a lot of research. i always wondered if you could buy testpipes and a 2+2 catback and then they will bolt right up but no one has given me an answer yet. also, about the drive shaft, i always wondered if i could use my driveshaft but i havent found any information on the size differences between the 2 transmissions. so basically i am going to just try it and see what works and what doesnt. then i can report back to people and tell them what can work and what cant.