I got the depstech endoscope today from Amazon and from what I could see the exhaust manifold seems go be leaking quite bad from one area and there's many more sooty marks around the rest. However, I'm really confused as to why the smoke occurs only sometimes, after my motorway run, no smoke, back on the motorway and checked, nothing. However, on my small town runs it smokes, if anything I was actually expecting maybe the valve cover to have a hairline crack and now and again the oil seeps onto the exhaust manifold.

Here's a video of the endoscope,


4:57 shows headgasket, looks fine.
7:15 valve cover at the back left going around to exhaust manifold looks dry
8:40 soot around manifold

https://youtu.be/RXLfDiGnvtk