12mm head??

[Dave]

Also, 12mm head delivers a hell of alot more fuel, it's not done in a linear form you have to multiply the area of 4.5mm radius area for 9mm, 5.5mm for 11mm and 6mm*r2 for 12mm in perfect reality. This gives chronic fuel when you don't need it, and quick injection durations. It's only useful when you need to sustain Rediculous fuel at 6k+ due to a larger fuel window into the high pressure head, it's just not needed for anything below that 11mm is fine, not to mention it'll destroy the timing of the pump. Give it a whirl though they sound "deeper" but will find an 11mm will yield better performance.