<<< There is no way to put the VEMS uphill from the throttle body in the car, so this will not be preventable. Any kind of goo trap will act as a pressure sink and slow down the response of the sensor, correct? >>>
Failing any uphill mounting, you should at least have the MAP hose go "Low" then "High" as it goes into the VEMS. This way, if there is moisture in the hose, at least it will not be allowed to rest against/inside the MAP sensor.
Where is your ECU mounted?