Diesel Dog, several have chimed in here and TMTT hit it on the head. If you really want the warranty leave it alone.
As for 275's yes it will void the warranty, they arent the stock power injectors. While it might be approved by Cummins, your warranty isnt with Cummins, its with DC. That being said I had 275's and the dealer drove my truck with them and I dont think they knew there were in there, I had no warranty problems. IMO, if you blow a block up or have serious engine trouble I bet they would check the injectors out (flow test) but if you are in for a broken cupholder you are probably ok.
I talked with the service manager at my new favorite dealership the other day about bombs. He is a long time Ford service manager and has since come over to the light

Anywho, he said there are 2 types of dealerships: 1. that goes out in search of finding the bombs so they can catch you and void the warranty. 2. The blind type that tends not to see so well and unless the District Manager from DC is in the store, stuff gets done.

Hence this is my favorite dealership.
My last visit I was in I told em if they could do it under warranty then great, if not I understand. I left all the goodies on the truck and I think being upfront with them mighta had something to do with my luck there. Oh by the way, he showed me how they check with their diagnostic testers to see if there was an EZ box on it, way beyond my comprehension but they know if they want to know. Know what I mean???