Originally Posted by V8Killer

You need to research the laws in Canada to see what law protects you as a consumer. There is one here in the U.S. I can't think of the name as of right now, but it is to protect the consumer in a situation of this sort. In any case where modifications are put on a vehicle and there is a malfunction of any sort the dealership can not blame it on said added parts. i.e. installing an after market exhaust then all of a sudden you have electrical problems. The two are not connected but some dealers like to push the unknowing consumer around and say your warranty is voided b/c of the mod. If you are that worried about it I would remove said parts and put the factory parts back on.
Also included in this act the company must prove that which exact part did what damage. I haven't had something this severe happen and hopefully I won't but I'm sure like most people here they have had their disputes with Nissan. Keep your head up and you will get a new engine. Worst case scenario if they can salvage your engine they will which isn't a bad thing either.