I’ll just tell you my LTZ 2008 did the same thing and the cam was shot. This is apparently due to the AFM system that turns the cylinders off for fuel conservation from my research. I bought a crate GM 5.3 and had it installed by the dealer. It was around 8k. The vehicle to replace with a like vehicle would be 80k new. I love the truck and yes it has its problem that I fix as they become an issue. I will keep this vehicle for the foreseeable future as to replace it I do t know what I have. Order the door actuators and get the tenant rebuilt when you get a new or rebuilt engine. I also had the dash problem. There is an excellent hard dash replacement kit that looks like stock unless you look super close. It’s a comfy car to drive but I’ll not ever get another car payment especially for one these days. Lots I can fix on this one for $1000 a month car payment and the vehicle takes me to the same place I would be going in a 80k car. That’s just me. I don’t need an expensive car to validate myself. Just saying. I also added a bypass box so the new engine does not go into 4 cylinder mode and it has not effected my gas mileage enough to be significant. Msg me if you want the Amazon numbers for the replacements I have put in my vehicle. Cheers