What is your understanding of the Act and its limitations [0]?
Here's a legal view that explains it further [1].
Basically, they can deny warranty service if you make modifications, and they can tie it to a failure. You can add 100s of HP to your engine profile with these things, and why would it be reasonable to expect a manufacturer to warrant related component repairs if they're pushed beyond spec?
Here are relevant quotes, and []'s are mine.
> The Magnuson Moss Warranty Act requires manufacturers to honor their warranties and auto manufacturers only warrant their vehicles against manufacturing defects. Your claim here could be denied because the failure was not due to a defect in a factory component. It was caused by something added to the car[...] That system caused a non-defective part to fail. Your mod did not void the [entire] warranty. It’s just that the failure was not caused by a factory defect.
> Obviously, an aftermarket camshaft or a hopped up ECU won’t void the entire warranty on your car. The master cylinder failed? The blue tooth quit working? Unless there is a logical connection between the mod and the part or system that failed, you should be good to go.
[0] https://en.wikipedia.org/wiki/Magnuson%E2%80%93Moss_Warranty...
[1] https://lehtoslaw.com/will-modifications-void-new-car-warran...
