IIRC, 2004 was the first year of the "non slappers".
I have a 2004 with a 5.3, and am just stunned as to how much more "get up and go" that it has, when compared to my buddy's 2004 F-150 with the 5.4.
I change my oil every 5,000 (or so) miles with Pennzoil Platinum 5w-30 and a Wix filter.
Dad has a 2000 Sierra with the 5.3, and it slapped with 5w-30, but Platinum 10w-30 made a significant difference. As far as I'm concerned, problem solved.