I think that the reason I get such a bad reading is that the part that you screw into the cylinder head does not have a bolt head' but a thumb grip. This means that I am unable to sufficiently attach it without removing the engine cowling, also if I do try and tighten it up I'm worried I wont be able to remove it.
I did the same test anyway on my Lui and got the result of 25psi..
Looks like I have a useless bit of kit and should have bought a different one. I wonder if its possible to just get the head plug and not buy the whole thing again..
