could be the check valve on the oil filter isint seating properly, I've had this with other cars in the past. A new oil filter may fix the oil pressure light delay in going out on cold startup.
Local service manager told me in the past he's never seen an oil pump failure or engine damage as a result of a poor one on an LC, any oil feed problems revolve around blocked oil pickup (injector washer problem) and this is often compounded by lack of servicing.
Sometimes I think I have a slight metalic top end noise at 2,250 rpm on motorway while still getiong up to full temp but if I listen hard enough I'll hear anything I want (or dont want) to hear !!!