Hello everyone!
I traded my first car for a 98 ranger 4.0 ohv. I got the truck and fell in love with it and have been having fun fixing it and learning a ton. One day the truck threw a code for the crankshaft position sensor, I cleared the code expecting it to come back but it never did. A week or 2 later it wouldn't start. I immediately replaced the cmp, but no luck. Then I replaced the coil pack. The coil pack made it start up and I drove it for a few months after that. I always noticed however that it had a rough idle.
A few weeks later it blew the head gasket. Long story short after tons of diagnosing and determining thats definitely what it was (overheated due to loss of coolant) I decided to get new heads and head gaskets. Did all the work myself replacing heads with brand new stripped ones. Got valves ground and lapped them properly. Replaced valve springs and all gaskets.
After that rebuild she was back on the road but still idling rough. I was able to hear a random pop pop sound from the exhaust at idle once she had warmed up.
In effort to fix what I assumed was a missfire i replaced spark plugs, plug wires, ignition coil(again with a oem motorcraft one), fuel injectors. And i had a bad fuel pump check valve so I replaced the fuel pump. Still no luck on fixing the missfire.
I scanned the ecm and noticed missfires on all cylinders in the test value but none with enough misffires to throw a code.

Things I haven't replaced and could be suspect.

---MAF(was cleaned and live data looked okay but. not sure)
---02 sensors (live data read and looks within. range, but could be slow)
---IAC (pulled it off and cleaned it and verified it. worked by unplugging and engine almost. stalling)
---CMP (replaced with a non oem from parts store)
---Camshaft synchroniser
---timing chain

In regards to the cmp i did some test with it unplugged. Idle didnt change at all when unplugged however there was a difference when revving it. When the cmp was unplugged and I revved the engine it would almost go down in rpm for like a split second before shooting up. Whereas when its plugged in it shoots up immediately like you would expect.
Other than what seems to be a missfire at idle the truck runs really well. Only 135k miles and for 1998 truck going pretty strong. I daily this truck to and from college (electrical engineering) and work. The missfire doesnt really cause many issues for me just really upsetting that I spent so much time on this engine and it still is not running perfect.
I was considering going after the cmp and cam synchroniser next but I just dont believe that it could cause this missfire. Any experts on this specific engine would be a huge help.
Thanks for anyone who can help.
I attached a video so hopefully you can hear the pop pop sound. I do have a magnaflow muffler after the cats so she is a bit loud.