[Critter]

I don't know if it matters if the airbox is on or not, but I do know the throttle needs to be wide open. The oil is to see if it is valves or rings. In your case it would be rings if the test had been done with the throttle open.

 

[Critter]

it would cause a lower reading for sure. Only you can decide if it is worth spending the money to rebuild it.

(though I had sent this yesterday)