I have used borescopes to do internal engine inspections maybe 10 times over the 25 years I have been in the business. It is difficult to interpret what you are seeing in the scope and to draw reliable conclusions about whether or not some scratch, line, or shadow requires the engine to be disassembled for repair. One time I was certain that I had a cracked piston, and had the head removed, only to find out that the "crack" was a carbon deposit.
Cylinder bores are difficult to read because they are highly reflective, and the glare can totally obscure the cross-hatch pattern. If the light supply can be adjusted to reduce the intensity, that would be a good feature to get. Another nice feature is a right-angle mirror that snaps on the end of the scope.
In the cases where I used them, borescopes provided another piece of information in the decision to continue or stop a test. Other inputs such as degrading performance, high wear metals in a used oil analysis, high blowby, or a mechanical noise had prompted the investigation in the first place.
