Hey guys, I have a 01 c70 2.3 5 speed. I’ve noticed from since I got the car that randomly but not frequently the rpm will drop at idle or surge for a second but I notice it the most after driving for over 10 min. But now I have a new problem, I changed the oil today (5w30 full synthetic) and when I shut the car off within 4 seconds I hear a faint pop coming from under the hood. Kind of sound like a burst of air. Just a quick pop. I’ve only heard it twice today. Only mods I have on the car is an intake and exhaust. Anyone have this same issue or have any ideas?