I've got a very similar story. I got rid of a Phantom BA XR (n/a though), then stepped into a TS (again n/a)and now drive an FG turbo. The missus still has the Territory but I fitted a catback Redback system to it in my driveway. Was a pain trying to get the old one out and the new in as the r/h rear of the car had to be jacked so high to be able to feed the rear muffler/tailpipe section over the diff cradle. Not impossibe, but very fiddly. TT would be harder, I would imagine, having twin pipes. Best of luck with it.