[tmoss]

The restriction in the stock intake is the lower. The upper flows in the mid 190cfm range by itself, but add the lower and that falls to about 140cfm. I've ported well over 100 lowers and can get that total flow up into the 180-190cfm range.

A stock Cobra/Explorer/GT40 flows about 205-210 cfm stock. Porting those lower will get you into the 240-250 cfm range. Paste the link in my signatire for more info.

Match the flow of the intake to the heads your using.

I would use Extrude Hone only for an upper intake where you cannot get into the runners to port them out. EH cannot selectively remove material in the lower where you want to re-shape the runners walls for best flow. I have pictures of EH lower ports and my hand ported lower ports - the difference is obvious.