Ford Ranger ticking noise after shutting engine off?

I have a 2002 Ford Ranger Edge 3.0L

I have just noticed this problem after replacing the Lower intake manifold gaskets and fuel injectors that after shutting the engine off, you can hear ticking/popping noises coming from the engine. I replaced the fuel injectors with a remanufactured set I got off eBay.
I followed the repair manual, the only hiccup I came across was removing the push rods, but I torqued those down to spec while reassembling.

The truck starts okay, it has developed a slight stutter when turning on. Sometimes it cranks longer than it used to. It accelerates fine. No noises while driving. Only when I shut the engine.

I checked the dip stick and it reads somewhere in the middle of the cross hatch, so no coolant leaks internally.
It is however, leaking from the timing cover, something that is common with this engine and it's been like that since owning the truck for a year now.

Feel free to ask more questions and thanks in advance

I have posted a video of the noise below

Added (1). i'm familiar with the exhaust popping noises when it is cooling, but this is different and it wasn't doing it prior to the repair.

Just the sound of metal cooling.

Isn't tat the metal contracting while its cooling down? All cars do it.

Exhaust system cooling and contracting. Quite normal.

Metal does this as it cools off.

Worry about engine sounds when the engine is running.