[ainarssems]

I was suggesting the old oil trick to Ranj. It is not conclusive but does give idea if it's more likely to be piston cylinder or head/valve problem.

How much is the compression difference?

When you say no fault code are there no codes at all not even for misfire? Does it show misfires in measuring blocks?

You do not need expensive camera/borescope to look inside cylinder you can make one out of old laptop webcam which you can pick for less the £10 from e-bay if you do not have donor.