02 'burb funney smell

Hello - My suburban has a funny smell. It smells like oil on the exhaust manifold. There is no smoke, no noticeable leaks, no oil consumption.
Nothing funny in oil. Nothing funny in coolant. Breaks are fine, no squealing. Trans fluid level is where it should be as well. Temp gauge doesn't show hot. No idiot lights. Seems to run fine. I do, and have always had, piston slap when cold for a few minutes but the smell is new.
Any suggestions as to what to look for?
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