carmax warranty question

[kachup]

guys i bought my truck from carmax and they sold it to me with a extended warranty, When i was shopping for a truck i noticed another 09 king ranch in the lot with a edge tuner and dpf/cat delete. And their was a 2010 f350 with full exhaust but i didnt see no tuner but soot would come out when reved up.
i bought my truck bone stock and i tuned and i did the cat/dpf delete mod. still got stock exhaust
You guys think they would void my carmax warranty because of the simple mod. Or should i say i bought it with the mods.
One of the manager told me they are mod friendly but i cant put anything that would harm the motor like nitrous or open the motor or upgrade the turbo.

the reason im asking because i pulled the transmission fluid dipstick and their was like dirt on it idk why, the truck runs 110% fine but i dont want the tranny to break, so i want to take it in to check it.

has anyone has been in this situation ??