The classic/original 3 BAR MAP SENSOR. Originally made by General Motors to monitor boost on the 1989 Pontiac Trans Am 25th Anniversary Edition with the turbocharged 3.8 V6 motor. Ironically this sensor was used only for the gauge, and not for the ECU. However it didnt' take long for tuners to realize the true potential of this part. Accurate up to 29 psi of boost!