Typical dealer response that to keep your warranty, they have to do the install. That is 100% untrue.
Read the Magnuson–Moss Warranty Act.
The manufacturer would have to prove that a part or the improper installation of the part caused the failure of a covered part.
That is why I do not use tuners, intakes or any other part that changes the factory parameters of a vehicle that is under warranty. It is too easy for a dealer to claim the part caused the failure. If you disagree, you have to file a breach of warranty complaint with the FTC or in some cases go to court.
As far as installing factory parts, no reason not to do it yourself if you have the ability.