([PID.2339]*9.369)-([PID.2340]/6.895)-.53
2339 as written in this formula is sensor voltage. That is why it's multiplied by 9.369 to achieve it's PSI counter part.
2340 as written in this formula is KPA. Dividing KPA by 6.895 gives us PSI.
I'm not sure as to why there is a -.53 on the end though.