I've also seen oil leak from the O-ring connecting the two sections of the Y-pipe, but it typically drips down onto the downpipe and makes smoke.
I think it's just the Y-pipe coupler that's tired and has some oil residue around it. Either get a 2.75" ID silicone coupler and replace it, or get an Efini Y-pipe setup for $240. The coupler would only be about $10 and wouldn't give you any future probs, but the Efini pipe is a bit of a performance increase and is WAY better designed.
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