I purchased a Brand new Chevrolet Silverado 1500 LT Z71 in2015. While still paying on this vehicle I had an issue with the engine bogging down and it would almost die. It would jerk and shake terribly to the point it just shut down. I took to Royal Chevrolet and they found that it had a broken Valve spring on Cyl 7. This went on and on they had this vehicle for a total of almost 7 months before they put 1 last engine in it. The 1st thing I did was drove down From Michigan to North Carolina to visit my daughter. Plenty of Mountains and a lot of driving as I drove 14 hours straight by myself. The engine that they had just put in started Chugging and choking and it stalled on the highway going through the mountains and I was hit in the rear end and the other driver never stopped. I managed to get it running again. Prior to leaving for North Carolina I ordered what they call a tuner where I could deactivate the AFM system and stay in 8 Cyl mode at all times. I had it sent to her house. I installed the program. Keeping in mind #1 I was rear ended. And every single time there was an issue it was Cyl#7 on all the previous engines. I talked to the Lead man at Royal chevrolet about all the issues and he said they know all about it and its a joke. They tried it on Cadillacs back in 1975 and recalled every one of them and turned it off. On my way back home not 1 single issue in fact and I sill have it displayed on my dashboard I actually got 26.2 Miles per gallon in V-8 mode in the mo