How does this add on the 8-12 Hp it claims in the description if you already have a custom dyno tune and full bolts on? I've always been told upping the MAF sensor size on the 4.6 2v does nothing gains wise.
The HP increase claims are based on a stock car and replacing the Original mass air meter with this unit. These mass air meters are larger in diameter and have a more specific calibration that an OE Air meter. Since your car has already been modified and tuned, you may not see the full 8-12 horsepower gains that a completely stock car would.