Reason I say confirm it with nissan to be safe is that The gtr specialist in aldershot stated that the gtr is the only nissan car that officially permits a modification to the exhaust system, and only I believe the cats but can't remember specifically, without invalidating the warranty.
After all the car is no longer standard and if an issue can be tracked back to the exhaust then it would be fair for nissan to not support that warranty.
Now in the real world many people do put exhausts on and warranties still stand so you should be fine. I changed my exhaust and had no issues with warranty work, but none of the issues related to the exhaust. I'd do it again sure but it was interesting what the salesman said about the gtr and the warranty stating explicitly that the exhaust could be modified with no impact on cover, unlike other nissan a.
just saying might be better to confirm up front and be safe just in case.