I’ve noticed - when I start my engine, my car idles low to high between 3rpm-1rpm. It goes back and forth for about 5-10 seconds before everything mellows and stays in the 1rpm range. Is this normal? I cut off my resonator/muffler and now I hear all those new noises I didn’t hear before when it would idle like this. Not sure if it’s just my engine warming up and parts starting to move or something else. Any ideas?