Hello my car fully warmed up idles at -22 vac. Sometimes it flickers to -20 vac on the aem boost gauge for a split second. When the fan turns on the vac goes to -20 through the entire fan on cycle.

Looking at the tial chart I should go with the brown spring but since it flickers to -20 sometimes I am not entirely positive as to which one to go with. I don't want to get turbo surge since the spring would be too stiff. Stock turbo and stock cams. I am on SD as well.

https://futuremotorsports.com/wp-con...image3085.jpeg