ZCarMan

Find a dealer and ask them first. You will want to find one that is mod friendly. Some will tell you if you install a set of intakes that it will void the warranty. Not necessarily true as it depends more on if what modification you added caused the problem you are seeking warranty coverage for. If you find a dealer that is mod friendly and understands mods they will work with you, hence the need to search for one that understands. Basics mods, such as high flow cats, exhaust suspension upgrades should be fine. Intakes should also be fine but again, who you work with at the dealer is worth finding out before.

Personally, I've added oil cooler, intakes, intake manifold, HFCs, CBE and have had no issues with my Z in the almost three years I've owned it, but I also have my work done at a local shop vice Nissan service. Good luck!

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Jon