I'm getting close to finally pulling my finger out and upgrading the exhaust on the Patrol. I spoke to Nissan yesterday and they confirmed it will not affect my warranty as long as the exhaust isnt the direct result of any future problems. I was hoping someone with some mechanical knowledge (of which I have none) can give me a list of problems that Nissan may claim are a result of a new exhaust, and are these costly fixes. Our dealings with Nissan since we got the car have been quite positive, they have been very helpful, particularly when we had a couple of warranty problems. Cheers.