fluctuating

Hey ya'll, when I got into work and parked up in this South Florida heat I noticed her making a little shimmy and reached 15.0 before dropping back down, and then it kinda continued. Is this somewhat normal in a 2019? I've only owned a 2016 previously with the Gen 2

I own a 2015 manual GT with 33k miles on it. I have roush AB with X-pipe installed since a year ago and everything was normal. However, when I took my car for an oil change about a month ago at the Ford Dealer, I started noticing that when I turned on the car on a cold start the rpm went to...