I also got this. I have noticed rust forming inside of the frame rails. I have a 2010 ls swapped coupe and a 2013 2.0 and got letters for both. I'm nervous that the dealer will do a **** job undercoating and if there is already rust my guess is they will just blast over it with undercoating and make it worse. I doubt they will even let the ls swapped one in but I may give it a shot. I'll see if they will do just the cavity wax and no undercoating. I plan to go to the Dealer in a couple weeks to talk to the dudes that will actually doing it to get a feel for their intelligence.