hi, i recently got myself a 95 wrx import. it has a boost gauge fitted which measures inhg when its ideling and boost psi when driving. when i first got the car it idled at 20 inhg, but it has been slowly dropping the last few weeks and its now at 5. i had no idea what inhg was so i googled it and found out it measures the vacum of pressure in the manifold i think. thereare no obvious problems with the car so does anyone have any ideas on why the pressure has dropped?

 

seems like something is not holding the pressure any more ie, hoses may be split or the inlet manifold gasket may need replacing, have a good look at all the vac hoses and give them a tug if nothing is amiss it may well be the inlet gaskets,.