Glyn

You could try to capture the sync shift at different rev ranges (if you havn't already)

But I think you have got enough evidence to justify pulling the rocker cover and measuring the tensioner petrusion.

Have you cleared the code and the code has come back while the vehicle has been in your possesion?

Also is your crank signal taken at the ECU or sensor. It might be worth while just putting a channel at the sensor and a channel at the ECU and wiggling the wires while comparing.

good luck
James