The service manual is a little confusing about the X-distance. It says to use the tool 54829001100 and then measure with a feeler guage - ok no problem. But then in the spec it says 0.10mm between upper edge of piston to upper edge of cylinder. So if the spec is really correct, then the special tool must be the exact dome height of piston (measured from the upper edge of the piston to the crown)?