"About SVT heads being Extrude hones already...Many peolle think extrude honed and porting are the same...the polishing part and the extrude honing are equivalent."
Depends on how much "Honing" you do
Mild Extrude Honing only removes surface "flaws" and givers a rough polish. This is what the "single Honed" 98 SVT upper intakes have.
Moderate Honing gives a more mirror like finish and does mild porting (increasing port diameter) say 1-2mm. This is what the "double Honed" 99-00 SVT uppers recieved, as well as the cylinder head intake ports.
Extensive Honing can be done to really open ports up. An example here is the SHO-Shop 37mm upper intake (sent to Extrude Hone). The nice thing about Extrude Hone porting is that because the silica-putty material flows through passages like air, metal is preferentially removed in areas of the most restriction to flow. Hand porting doesnt do this (not to say it is bad).
