Recently I've bought a 2016 Dodge challenger SXT Plus 3.6L V6, automatic. I've been having issues with my gas mileage. I'm averaging around 17mpg, and I've also been having issues with acceleration, sorta like if its stuttering when I accelerate, which later goes to normal. On rare occasions the care will shake very lightly when idling. I've been doing my own research to figure out what exactly is causing these issues. Based on what I found its either I replace the spark plugs, air filter, clean the engine throttle, replace ignition coils, or that the transmission is failing/slipping. I'm also trying to figure out what are the best spark plugs and ignition coils I can purchase that would be the best for the vehicle, regarding the proper gap size and so on. I've checked multiple websites for the proper gap size for the spark plugs and everytime it offers different sizes varying from 0.043, 0.044, and etc.. If anybody knows any information/solutions, please let me know as detailed and accurate as possible. Thank you.