At 30psi the Swedish items have been flow tested to 2% disparity between cylinders and on ALL of Harvey's 600+bhp conversions is his plenum of CHOICE .

These are the ONLY ones that I know of that have been engine dyno developed. Make of that what you will, but I personally think you'd have to be stupid to put a £200 "copy" on a £10k engine . Get it wrong and it's hasta la vista engine .