Sorry up front about the massively long post, but it covers my experience and something similar to this would have been helpful for me about 12 months ago. Should stress, not trying to convince anyone of anything, but I wrestled with this same issue for months when deciding to go catback or engine-back. Mods obviously feel free to delete this post.
Firstly I bought my SS (June 2017 build) as a daily as I've already got another project car that I enjoy on weekends etc.
However, and this is obviously a personal thing, I quickly felt regularly disappointed that I wasn't getting the full bang-for-buck experience that I wanted from 6.2l V8 in terms of the exhaust note.
Was initially thinking catback to preserve warranty, but then read the difference headers and cats can make to the note - deeper being one of the big drivers for me. Listened to a few cars that had either option and it pretty much convinced me that if I'm going to do it I'll do it properly and get exactly what I want. So I was at the point of either doing it full-on, or not doing it at all. Also niggling at me was the fact I would have to wait for several years due to the warranty to get essentially what I wanted when I bought it in terms of exhaust note.
I then went to my local Holden dealer and was upfront with my dilemma, what I had planned and what it would mean in terms of warranty. They categorically said as soon as the tune's been touched pretty much anything warranty-wise in terms of engine/clutch/gearbox/diff will be an issue/void in terms of warranty.
Then went to my preferred tuner/workshop where I was going to get the work done and had a chat with them about the same dilemma. And yes, I know their aim is to sell their product/service, not turn people away with fears over warranty.
Interestingly, both said the same thing - if you've got more than about 20,000ks on the motor/driveline without issue or warning signs so far, and you don't abuse it mercilessly or drive it too hard too often (and have some mechanical sympathy), if something was going to break/fail, it would have happened by now. *obviously there's always the random fault/failure that can still happen with anything mechanical , so it's a risk.
So I bit the bullet and decided to go ahead with an engine back exhaust package, otr and tune.
Before I did it, I went back to my local dealer, told them I'd made my decision and as a result wanted a final service (earlier than scheduled service/checkover) before going ahead. Again, I know it's not in their best interests to find fault when its under warranty when they know the driveline warranty will essentially be void in a few weeks. But I felt better being upfront.
I've since had the work done and for me personally it was worth every cent, and the risk of no warranty.
I still chuckle to myself when I give it the beans in terms of how good it sounds and how much better it goes. In fact I leave for work early every day just so I can drive it that bit more - almost look forward to going to work.
For me personally, I have absolutely nil regrets.
