What most people fail to see is the fact that non-SVT heads are a bottleneck as well.
There quickly comes a point of diminishing returns with any mods in front of the heads when they are now the restrictive point.
I stated long ago that most people expecting large gains from any UIM or LIM work are going to be disappointed. It takes more then just upgrading one piece of the puzzle to get good results. Every piece needs to be integrated into an overall design plan and don't skip the detail work.
FYI - I'm sure SVT could have asked for a little more time on the Extrude Hone bench if they thought the UIM needed it. Then remember the SVT heads are extrude honed themself and the engine uses a larger LIM & TB to boot. The port size difference between stock and SVT is very notable!
Then take into account that the bulk of the gains from the extra airflow ability are at high rpm. When I put on my max honed UIM my gains were notable above 6000rpm. The stock cams are already dead and buried by 6000rpm. The small low rpm velocity loss may actually hurt the stock cams.
