OK after checking this out apparently the Pro comp heads arent the same as Pro top line or Pro action heads , Pro comps are china made and the others are made in Australia. Thats why I couldnt understand all of the squacking because I was impressed with the as cast condition of my Pro action heads, they flowed 375cfm at 700 and 390cfm at800 , at 28* right out of the box. Oh, that was with 2.3 intake valve and 1.9 ex. After a prof. port job they still just made 400cfm although they picked up alot through the mid lift #s which means more than peak flow # s. got to go to work, be back on here this evening.