If you have FCP5, export to soundtrack pro & normalize there, if not, a copy of Peak Express should have come with your FCP 4 or 4.5. That has a normalize function, but be very clear that Peak is a destructive editor, whatever you change will be permanent. I suggest making a copy of the file you want to change and retain the original in case of problems.
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G5 Dual 2Ghz <> 4GB RAM <> FCP 4.5 <> Kona 2
ATTO 42XS <> Huge Systems 1.25 TB 4105 Fibre