i have a 98 gst 5spd and always vac at 19 idol and then when driving and let off i vac at 21. but sometimes when i drives it vacs at 24 like its should and drives smoother. how do you do vac leak test??

 

Get a vacuum pump from autozone and connect it to a vacuum nipple or do a boostleak test. In other words, you can push the air through or suck the air out, your choice, but both achieve the same results. One is just quieter than the other. lol