I work within dealership service departments as a consultant, around the process more than directly in it. The dealer wouldn’t warranty related systems if effected by the mod. For example if you swapped in a set of Deavers and had issues with the rear u-joint on the driveshaft failing, or swapped in eibach springs or a collar and had CV issues, an argument could be made that the mod exacerbated the problem by changing factory geometry and the claim could be denied. If you have a tune and the power seat fails the systems are unrelated and there shouldn’t be a problem. Certain things on the engine, like a water pump or alternator, shouldn’t be effected by the tune, but turbos and injectors and the rotating assembly itself would be.
Ford and all of the OEM’s are trying to reduce their warranty liability. Ford has $5 billion in warranty liability currently according to an article I read about the 2021 F-150. They routinely audit the dealers and will back charge them for repairs without proper documentation, not enough time clocked on the repair, cores not returned, or other suspicious circumstances. A bad warranty audit can cost a dealer 6 figures. There is plenty of fraud happening, both intentional and unintentional, costing OEM’s millions.
I’m purchasing a very long extended warranty through Flood Ford to protect my investment and reduce future costs. I’m planning some mods like a set of deaver +2 and a rear bump stop kit, but nothing that would effect the engine warranty. My bigger concern is all of the electronics in the 802A I ordered. I don’t want to be paying for repairs on the climate control system, vehicle dynamics electronics, 360 camera, etc. The live valve shocks and 10 speed trans are also big ticket items, hopefully Deavers wouldn’t effect the warranty on the rear shocks.