Checking for carbon deposits
 

Have a tricky code and lights with my 2013 XD even the mechanic said he wasn’t sure? Anyways I am going to check for carbon deposits with a borescope but I’m getting mixed info online. I know I need to check valves and piston head by going through the spark plug hole, should I look anywhere else or go in from any other angles? Some some through the intake manifold?
thanks !