LTFT help, please

2018 buick encore. I'm getting a reading of about 24% on long term fuel trim, at idle. Just recently got an oil change and personally checked the filter as well so the filter is good. All the hoses around the engine have been tightened securely. Im thinking there's a leak somewhere in the exhaust system, is that a proper assessment or an i way off? Also I was thinking of using a smoke machine, would that work to help me in this case?