Read my post above. I bet you what you are reading does NOT say PSI - it says Lbs. There's a difference.

The chart in my link above is for 2005 models, but I don't believe there was any difference on the '04's - you need to put 0 - 15 PSI in your fork in order to have 45-52 pounds (not PSI) of weight on your fork to preload it.

If you are not using close to the full amount of your 120mm travel on moderate to bumpy terrain, you have too much air in it.

It's simple really - add enough (or take out!) air in order to have 20 - 25 % of your fork's total travel used up just by sitting motionless on your bike (sag).