cat is an alias for Get-Content which is notoriously slow. If you do some googling people suggesting using System.IO.StreamReader instead. Have you tried that?
When I say cat I mean cat.exe, the unix utility. My usual workflow is
<exe writing to stdout> | <filtering/manipulation> | <exe reading from stdin>
Whenever I run this inside PowerShell, whatever flows through the pipeline seems to be cached in memory, and it is orders of magnitude slower than when I run the same pipeline inside bash.
