1992 Toyota 4x4 22RE with 196,000: Vehicle only can achieve 45mph. There is an internal popping sound when accelerating or revving momentarily. Sounds fine at idle. Spark to all 4 cylinders with two new sets of spark plugs. Distributor and rotor looks great. Cylinder #3 shows black dry substance on spark plug after running a while. 7 years ago a new timing chains and metal guide were install and head was redone. Check valves and adjusted as needed as well checked timing chain tension. Listen to fuel injectors (screw driver method) and all sound active. Could be #3 fuel injector but don't want remove intake and go that route until everything else is ruled out. Somewhat a newbie with these engines and electronic. Need help! So what could it be and what else could I check?

You can hear sound on video:

 

one of the popping noises is the "door" inside the AFM snapping open when you "punch" the throttle. you are hearing it hit the stops internally as it goes from slightly open to wide open.