we have tried out the h pipe with the touring axleback (mufflers that come with sport catback) and it really sounds the same. I think jayman33 would agree.
On my 12 I ran the car with LTs and no tune for about 2 weeks. I datalogged the car with the stock tune and it only ran a little richer. Not enough to do anything to hurt the car. I still recommend getting a tune as soon as possible though to optimize the car and get the most out of your new...