the MAP sensors are the same - 89-91 has a purge cut-off solenoid valve next to the MAP - 88 Si has the same purge cut-off solenoid and also has a dashpot control solenoid valve, which controlled idle when cold - on the 89-91 Si, they dropped the dashpot control and added a fast idle control valve on the back of the intake manifold - the MAP sensor is attached to the bracket with a couple of screws - you don't need to swap everything in order to swap out the MAP