yeh i meant the extractor mounts... it's hard to explain here, simply i would put it as atomisation, i was having a pretty in depth discussion with my dad about it who has done all this flow bench stuff etc... it's pretty hard to explain without pictures and im pretty computer illiterate so yeh.. also 20v heads are pretty productive already so it is going to be very hard to get any gains without a flow bench, good example of this is old honda 750 motorbike heads, after porting slightly then a little bit more the power does go up, then after a little tiny bit more like a tap if you want to put it that way. power decreases, not sure also if your ports are all EXACT... i have pretty much gone off track here but anyhow