Hi, i was bored so I made an EXPERIMENTAL SIOC script for a Brake Pressure Gauge from OC.. you can try it if you like it works pretty good and even smooth on my set up..

it is for PMDG767NGX uses its FSUIPC offset

one thing to mention is that your servo should be at (approximately) position 1024 with needle at 0PSI and position 325 with needle at 3PSI

so yeah if you have this AC and this GAUGE try it out if you like OH almost forgot Output # must be changed to where you plugged in your servo on the OC servos card

Code:
Var 1, name servo, Link USB_SERVOS, Output 2, PosL 0, PosC 511, PosR 1023

Var 2, name gauge, Link FSUIPC_IN, Offset $6578, Length 4


 { 

  L0 = 0.0000000000007423461051269044 * &gauge
  &less = L0 * &gauge
  L1 = 0.0016731854124129018 * v2
  L2 = L1 - &less
  &SERVO = L2 - 941592.5023169761

  }
  
  Var 3, name less
i came up with these numbers figuring out the quadratic equation.. hmm that sounds geeky... so that is why it depends on your servo position, i am assuming that everyone would have the same fsuipc offset value regardless

PS there probably is a better way... idk...

Andy