I have 2018 STX with the 5.0. Currently has about 66k miles on it. For about 2 months or so. Everytime I start it up from a cold start, it goes from out 1300 rpm and instantly starts climbing to just under 2000 rmp. It slowly comes down a but and then there is a single loud knock from the engine and rpms go back down to 1k. I don't know what it is. It's always served regularly and just had its spark plugs change and it still does the knock. At highway speeds, it feels like it has to work harder to stay up to speed. I've also noticed a vibration since this started. The vibration sounds like it's pulsing and depending and which high gear it's in will change how fast the pulsing sound is. Anyone else experience this and know what it could be?

This all started after I took it to Valvoline for an oil change and they also did the injector cleaner thing they do.