When you dismantle the UIM/LIM, you'll be amazed at the build-up of carbon and gunk inside. This has a net effect of narowing your air passages...causing turbulent flow...and restricting the amount of air going into the engine. By removing it all, you'll be restoring your engine to "like new" performance..kinda like when you change your plugs out.
Now if you go the extra step and match your UIM to your LIM by gasket matching and removing any material, and then optimizing your TB while its all off as well, then you'll actually gain HP. Heck...optimize your LIM...get more.
