the amount of vacuum (even though i dont like that saying) it pulls at idle depends on a few thing,,, (cams bla bla) so dont worry abut the number it if pulling,, aslong as there is a vacuum there your happy
the reason why i was laughing at -18psi,, is because the lowest pressure that is possible to create (nothing-ness) is -14.7psi gauge pressure ( or zero absolute) so minus 18psi,,, is more than nothing
everything in our would has an absolute zero,,, pressure being -14.7 psi gauge, and temp being -273 degrees c
below this temp, electrons stop moving and the atom does not excist no more
we really shouldnt use guage pressure,, as zero drifts on guage pressure,,, atmopheric pressure changes by the minute with standard atompheric pressure being 1.013bar absolute, or 14.7psi absolute