Stock parts to keep for warranty work

So, I've seen several posts on this forum where people have had to replace their mods with stock parts in order to get warranty work done by the dealership. The two so far that I've seen are.

1. Wheels & Tires
2. Drive Shafts

Now keeping the above is hard for many, but what kind of work has the dealership asked to have put back to stock? Also, what other parts have people had to revert back to stock besides 1 & 2 above?

Thanks!

Best thing to do is ask your local dealerships service manager what they require. I know if my dealer has installed the components it is covered under warranty.