3 valve heads
ntake
Lift----Stock CFM------CNC Porting CFM
.100-----77.1--------------75.3
.200----147.0-------------162.0
.300----199.6-------------228.3
.400----216.0-------------273.8
.500----223.2-------------283.6
.600----224.8-------------292.9
Exhaust
Lift----Stock CFM-----CNC Porting CFM
.100-----52.7-------------46.2
.200-----97.8------------104.3
.300----120.2------------135.7
.400----138.1------------163.2
.500----148.2------------177.0
.600----153.7------------189.6
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Not bad but I do believe the 4 valve heads flow better than 300 cfm stock (I can't find the exact flow numbers to confirm this as I dont have the time right this second.)
regardless in a game of numbers the 4 valve heads will always flow better so in my mind the extra time and less expense may be an excelent performance upgrade over anything else available for the 4.6 or 5.4. Not to mention the extreme response to simple bolt ons like nearly 100 hp for cams rockes and springs OR 50 hp by simply changing the rockers.
but thats just my opinion any head will work better than the non pi heads you currently have

. ABS I've been told is great BUT I have had some nasty experiences that i wont get into here.