The problem a YB on Weber management has is that the ecu is very sensitive to changes of a few millivolts which on other sensors are not really critical as they are all filtered electrically within the ecu and in the software to slow them down and just look at averages.

However, the map sensors signal is sampled every 90 degrees and recorded by the ecu so that it can build a model for each cylinder.

If the pressure suddenly rises then it assumes that the throttle has been opened and a transient fuel correction factor is tagged onto the injector pulsewidth to ensure no lean out occurs.

The whole system is speed density and that means its entire fuel calibration and delivery system is based almost entirely on map sensor voltage, so any variation in voltage output results in a fuelling change. This is why its essential that the signal output is a genuine reflection of manifold depression/pressure and not just a niose spike. Remember, we are talking about millivolts here, not volts.