I have shaved 20r heads an amount that I would rather keep as my little trade secret, but if you shave too much off of your efi engine you will cause your knock sensor to pick up combustion noise causing the ECM to severly retard your ignition timing.
To go any more than the factory spec, you need to move the knock sensor, and will be stuck running premium fuel.
If you are doing it to repair your current head, just buy a new one. contact cylinder heads international. If you are trying to obtain more power, consider other options and think about current gas prices before you make a decision.
