Ok, I need a little help. Was driving my kids truck and I noticed at the light I got a rough idle, along with a chug chug chug chug. SES light is now on....too late to go get codes read. It is acting like a cylinder is not firing. It is an air sound, and not an exhaust leak. Just had HG replaced with water pump, new wires and plugs, no leaks coolant level good. There is no metallic sound, no banging or tapping. Could my plugs or wires have gone bad in less than 1000 miles? They are not top end wires and not sure of plugs. I put "stethoscrewdriver" on valve cover and plenum and everything sound ok. Exhaust gaskets just replaced and noise is definitely from top. Vacuum leak? Bad plug(s)? Help.

 

UPDATE: I was pulling plug wires to check plugs and low and behold this little gem stayed on the plug. I crank truck up with wire off and it runs exactly the same. Number 4 cylinder was not firing due to bad plug wire. Or at least thats how it appears.

 

UPDATE 2: Plug wires changed no difference. See video link. It is NOT a tap or banging sound. It is air. I am waiting for friend with code reader.