Oh! I remember this post. I think what he was trying to say was to tight them a bit more. If there is a new official figure for 4Nm, then Mazda could possibly confirm it. But he went double that and fixed the problem.
I think you could add more torque but for me the message is something else. He is already on a second engine and the second engine has the same problem as before. So the minor details about the torque, etc, do not really matter. These engines are designed to last the finance period and then they die.
If you can put the car back together and it works, it is all good. Do the recommended torque, do a bit more, and see how it goes. You have nothing to lose anymore.