So my Forge BPV for my LGT came with 3 springs, a yellow, a red, and a blue; and two shims. It came with the blue one already in the BPV.
I did a little research online and this page says:
http://www.maperformance.com/forge-valve-spring-tuning-kit.html
Green - 5-15 PSI
Yellow - 15-23 PSI...