The only time Ive had an issue with it saying anything other than 98-100 when not running is when the sensor wasnt calibrated right. I have the 3 bar sensor and it was calibrated for 2.5, making my gauge read like 85% or so.

95 Eclipse GS: 10.5:1, Crower 2's and MSII
186 WHP - 150 WTQ
14.697 @ 93.85 MPH......Gone, but not forgotten
99 420A Avenger: Given to my sister
99 GS OZ: Sold
03 Evo 8: Family Car with balls