Recently I changed my oil in my 2000 Alero 3.4L and the oil had some milkshake color (light colored) in it. I did some researching and the majority consensus on the internet was the intake manifold gasket. I replaced it and in the process noticed the inside of the valve covers were plastered with yellowish gunk (antifreeze in oil?). I put the "Problem Solver" Felpro gasket in. I've been driving it awhile now and I notice there's yellowish gunk accumulating on the bottom of the oil fill cap and inside the valve covers again. Is it possible its still the intake gasket? I'm pretty sure I replaced it correctly (followed the Haynes manual to a T). Or is it a head gasket??

 

The yellow stuff is condensation. Oil generates some of it normally (and does so more if you just do nothing but short trips), but if there's a ton the coolant is likely mixing with the oil somehow. It might be your head gasket. They are as unreliable as the intake manifold gaskets.