Mine got milled and has raised compression... it requires premium gas but the power is lower than before. This may be a cam timing error (though we could not measure one), or maybe it's a problem with the stock computer program.
In theory this should raise power, but they say if you want to raise compression you should do it with the pistons, not the head... but then, some of the fancy heads they sell, like Esslinger's, are shaved this way.
It does not change your displacement -- that number refers only to the volume swept by the motion of the pistons, not to the combustion chamber volume.
