I Quoth:

Symptoms
Its very noticeable when first starting it up, seems to go away once it gets warmed up.

End Quothing.

My stock answer for anything that sounds like a lifter, but isn't a lifter is to tighten the exhaust manifold bolts Especially when it warms up, the sound starts going away, or lessens. Probably not even a bad gasket. Just loose bolts.