Cold engine clatter of the 4.0 VVT-i

Aside from valve train noise-which ticking is good-means valves are not to tight-Has anyone been able to isolate the clatter (almost piston slap noise) when the engine is between 1200-1800 rpms. Rule out main or rod bearings-that is not the noise-An Exhaust leak would not clatter on a 6 cyl engine-it would have a steady sound. It seems to emanate from the left lower drivers side-but not as far back as the bell housing. I have a 2007 2.7 (no noise) had a 2.4 no noise- Ran a 1993 Nissan (2.4) over 320K no issues- spent 20+ years pulling wrenches for Ford, GM -and VW
I've never heard this particular clatter except for Subaru 2.5 which was piston skirts redesign from 2011 til this day.

 

Does this only last for the first 1-3 seconds of a cold start up?