In the US, an aftermarket exhaust system cannot legally fully void your warranty. It will void your emissions control warranty, because I understand the Borla deletes a set of cats, and is supposed to be off-road only. While the legal mumbo-jumbo is pretty clear, what a specific dealer will do in a given case isn't. If you do a search on this site you'll see complaints about dealers refusing to service cars with aftermarket exhausts, threats of voided warranties, and other more minor stuff. Some annoyance, warranty-wise, could be a risk.