I know that I am a bit late to this party, as others have noted already, definitely, by all means, if you get any GM SUV that is cursed with AFM do a delete of some kind. There are electronic ones that shut it off, and there are also complete overhauls that replace the top end of the engine. My prior employer we used Tahoes for my unit. We had a 2007, two 2011s, two 2013s. So far the 2007 and a 2013 have had complete replacement engines, the 2007 at about 110K, the 2013 at 68K miles due to AFM damage, my 2011 had to have the entire top end rebuilt after the AFM decided to eat the camshaft at 70K. The other 2011 and 2013 have all had major repairs done to the A/C systems but somehow have avoided the curse of AFM destruction.
So proceed with caution when shopping for that body style. If you are lucky to find one with a complete service history and have had the AFM curse dealt with, you should be good to go. The LS engine is a great design, it is a tragedy that AFM was allowed to be put in it.