It can't -if your fuel pressure is correct and not falling below the regulator pressure, it won't change anything.
If your fuel pump (for whatever reason) can't keep up with the flow and pressure demands - generally at high load/rpm, fuel pressure will drop, and IDC would have been increased to compensate. Unless you're watching fuel pressure live as you do this, you don't know (but you could probably calculate it).
Obviously if you fix the fuel pressure/flow issue, your IDC is now increased vs what it should be, and you will run rich.
I've just done this modification myself:
