07-12 models have lifter issues. Some genius at gm ruined a great engine with the DOD idea. Have run into at least a half dozen in the last or so with issues. Engines will have a miss at idle speeds and a interesting kind of squeak/ knock noise. Surface of roller lifter will be pitted, flat spotted, or at time lifter will spin in bore and really make a mess. To replace lifters is n these the heads must be removed. So there is a lot of labor, and then hope the metal hasn’t caused other issues. Best fix I know of is jasper engines has a rebuilt unit that eliminates all the worthless DOD crap. Have done several of these and they run great. Jasper also uses a updated piston that eliminates the low tension rings, say goodbye to the oil use issues they have as well.