Jinx had that very same problem when I took delivery of her. Turns out the kid that owned her before me drove around town for quite some time on 2 out of 3 coil packs, which dumped fuel into the chambers, leaked down and thinned the oil. This in turn caused several rod bearings to spin.
Did you happen to check out techinfo on how to check the coil packs? And did you check the ICM plate for coil terminal corrosion? Even if it were the coil packs, it may be a moot point now as the damage may already have been done.
Welcome, downwardly mobile yuppies, to the dawn of the Age of Nefarious.
1993 SSEi - FrankenJinx - dead and gone.
1994 SSE (136K strong) - 180* t-stat,HD alternator, most unequipped SSE on the club, XM radio, Kenwood CD/MP3.
2006 Chevy Malibu Maxx LTZ - Custom 2.25" manifold-back exhaust w/FM-80. Probably the only Maxx with this system.