The unit works the same way as vag-com and uses the signals from the existing sensors, if your mods thake the actual values beyound the limits of the sensors then it is the limit that will be reported.
There are not many cars that hit the maf limit or any of the others, if few people running very high boost levels may hit the boost limit value but if your running very high boost then you are in dangerous waters anyway.
I'm not sure what the limits are on the mk5 yet.
MCPII did do a slatted vent pod for the MK4 in the US, but don't seem to be pushing it.