I really don't have any clue as to where you could get the factory flow numbers for the 1zz head, um maybe Toyota did some research on them I am sure before they put it on the 1zz but other than that, I am not sure. You might try calling some well respected machine shops that specialize in porting heads and seeing if any of them has done any research on a before and after head job LOL!!!! Thats about all the advice I can give u!!
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