It is still possible to get oil wicking up and sitting in the valley of the lower intake. Mines doing it..lol

Burning off the engine is typically oil, because the valve covers are directly over the exhaust manifolds. Seepage of coolant out the ends or on the LIM would usually not burn...more like a simmering.

Easy way to check your valve covers is use a papertowel or finger to wipe directly under the rear valvecover and observe. Wet/oily would indicate bad gasket. Front'* are visible.