2016 Malibu 1LT 1.5T/6-speed 6T40
These cars are direct injection. Nothing you add to the fuel will clean the intake valves. Top Tier Fuel, dexos1 oil (gen2/3), and the oil separator are how you prevent/slow buildup from forming in the first place. The service the dealer does is a chemical cleaning of the intake system. Chemical isn't as good as manual/mechanical but easier. Did they scope the intake ports? Some ugly stuff would have to be happening to catastrophically restrict the intake ports at just 78k. There are dozens of gen9 1.5/2.0 owners on this forum over 100k without intake carbon symptoms. I'm not sold on that as the cause here knowing the throttle body wasn't that dirty. The dealer has seen the car though, let them do their thing. Hopefully it works but be prepared for more work.