I have a 2018 Chevy equinox premier awd 1.5 turbo with 73,000 miles and it’s overall in very good shape - doesn’t burn any oil, shifts very smooth. There are no codes - not even any communication codes for all vehicle modules. When i accelerate above 20 mph I hear a faint whirring noise, but it needs all new tires and an alignment. Sometimes at idle at operating temp the rpm’s ever so slightly go up and down, but they don’t fluctuate over 100 rpm’s when they do. It’s like the needle of the rpm gauge barely moves. This is minor but still a small concern of mine. Could this be time for spark plugs? Lastly, The rpm’s fluctuate somewhat when coming to a stop. The fuel trim isn’t high but i’ve seen it go to -5%, doesn’t ever run lean, only rich but never over -5%. I change the oil every 5k miles with full synthetic and I plan on changing the transmission fluid next oil change as i’m unsure if it’s been done before. Where should I start?