question 1: don't personally have a clue
question 2: depends on which country you live in and how "friendly" your dealer is. In the U.S. there are those who will claim that Magnesun Morrison warranty act forces the mfg to prove the aftermarket device caused a failure. However, what most don't realize that MM only applies to aftermarket parts used in mfg defined normal service for warranty (e.g. filters, oil, other fluids). By the way thanks to MM you are not required to go to the mfg (dealer) for routine service to maintain the warranty. If the mfg requires you to use there service only, they must provide the service for free.
Mfg have the legal right to deny warranty claims for failures related to performance enhancing devices. (e.g.engine & transmission failures) It's a big issue on ford, GM, Dodge diesels since it is easy to add 150+ RWHP to there diesel trucks. As you might expect, that puts a good strain on lots of drivetrain parts, and an invitation for failures.
With gas engines, there doesn't appear to be near as much an issue, since your seldom going to get more than maybe a 10% increase in power, if that. Probably not enought to raise a reliability issue. By contrast, with turbo diesels a 50% increase in RWHP is pretty easy to do, at least on the big 3 diesel trucks.
So it really depends on how the dealer acts and how aggressive the mfg is. Some will fix stuff under warranty, others will not.
GM is now at the point on duramax diesels that they can determine if any of the last 10 ECM programs were non factory programs and if any were, drivetrain warranty is voided.
I'm sure some may disagree with my statement about MM applicability to "powerup devices" , but I don't think fighting a mfg is an easy task.