Was thinking about these filters for another project, and the Pierce site that there is virtually no restriction with the new mesh trumpet filters...
Why do you say disastrous? Do you mean they create turbulence?
Total airflow capacity of any filtering material is proportional to its surface area.
When the filter is situated directly in front of the velocity stack this area is naturally very limited compared to a proper filtering unit such as one shown here, (estimated 1500 square-cm on ITG vs. 150square-cm on stack screens) In effect, these screens should have filtering material that allows air to flow through the filter ten times more efficiently with same filtering capacity, which they do not have unfortunately. Furthermore, a screen directly in front of the trumpet harms airflow inside the velocity stack.
The difference in airflow is so high that going from these screens or meshes to a proper filter often requires re-jetting the carbs in case of weber, Solex addhe, Dellorto, or similar to get the engine run properly and reach its full power.
Cheers Andy