LTFT high at idle

My 99 GT auto with 80k miles seems to have high long term fuel trims at idle. Seems to be about 17-19%. Short terms look pretty good and usually hover between -3% and 0. It runs and drives well but occasionally is slow to start when cold.

I'm planning to check for vacuum leaks tonight but I'm leaning towards this being a fueling issue due to slow starts. Since I bought this car I've been refreshing things as it is my daily. I'm thinking I'll tackle the fuel filter, injectors, and plugs/coils soon. Hoping that normalizes things. Anything I'm missing or I should check/replace?

I did both propane and soapy water tests. Could not find a vacuum leak. Good tip on the frps. I'll check that today and then the fuel filter. If that doesn't solve things, I'll start working my way through the system.