Man I used to bump the **** outta triple six! That **** knocks! I wish I could have a more specific answer for you, but all
I can suggest is analyzing the track yourself. Playin' around with the EQ's, like turnin' everything but the bass down... Hell, try turning the BASS down! See what frequency it becomes inaudible at. See if it's easy to pinpoint, or if there's some harmonics to it... Like, are there sounds at different frequencies that accompany it to make it sound fatter? Does it have distinguishing aspects to it, like it was handmade in layers, or does it sound like something straight off a synth? Take something that sounds like a good starting point for recreating it, like a smooth kick with a long, strong decay. What does it need? A tighter attack? Fix it! Some pitch bending? Fix it! At the very least you'll come up with something unique, that you made yourself!
I don't use FL, so I can't help you there...
I know this isn't the answer you were looking for, but unless this is one of those <1% times when someone knows the exact answer, this could very well be the best advice you're gonna get here (not counting sirflex, who was quite specific with his theory

). Not that I'm a fsckin pro or anything, but in my experience these questions always seem to turn into 'find your own sound' -vs- 'so and so sampled so and so, and made a hit!' flamewars.
Anyway, I think I'll pop that CD in tomorrow on the way to work... If I have any thoughts, I'll track this post down...