96 7.3 idle fluctuations/ drops

In the video I am giving it throttle then quickly letting go. Truck is a 96 7.3 f250 4x4 auto, california model.

Sometimes at red lights the idle will drop and quickly return to normal. Usually if it happens once it will happen a few times within 30 seconds. More commonly happening when truck is warm. It has never died on me.

Last night after I got home I put the truck into park and the rpm’s dropped unusually low and then back to normal. So after that I gave the throttle a little touch and let go quickly and the rpm’s dropped further than normal, then quickly returned as seen in the video.

I’ve recently replaced the fuel lift pump and all the rubber intake and turbo boots. Also under very heavy throttle there is some black smoke, not a ton but wanted to mention it in case it could be related.

I have recently got a for scan reader just haven’t had time to hook it up to my laptop or know quite what I’m looking for with it. What should I look for within the truck or data to start diagnosing this problem?