it is an interceptor scan gauge. Allen Nelson has the hook up on them. It displays a lot of values like:
  1. OIL psi
  1. trans temp
  2. o2 readings
  3. timing
  4. Knock retard
  5. S-trims/ L-trims
  6. rpms
  7. speedo
  8. Maf frequency
  9. Maf per Lb per min
  1. coolant temp
  2. reads and clears DTC's
And ive probably forgot something.