The B side to Model 500 "Starlight" - the beats are buried deep enough into the mix to make it ambient that's a headphones track if I ever heard one
perfection in the form of plastic, nuff said.
I'd have to qualify tons of Jeff Mills stuff as ambient as well - most of the tracks on the Humana EP, the Other Day, etc. Mills usually has some great ambient tracks on his releases.
The Every Dog Has It's Day series has some great tracks, not ambient exactly but very melodic and blissed out. Some of it's a bit samey, but worth checking nonetheless. Track C2 on Vol 3 is probably my favourite.
D.