Oil leak
 

I have a 1995 SL500 with 27,000 miles and for some reason I can't find the oil leak. It came into my shop with the valve cover leaking because the customer had someone replace it improperly and it turned out to be a bad oil cap. I replaced the valve cover gasket and oil cap but I still have a small leak at the bottom of the bell housing. It's not the rear main seal. Anyone have any suggestions?

Is it in fact a leak, or could it be residual oil from the leaky valve cover making it's way south due to gravity?

I have had the oil passage plugs on the rear of the cylinder heads leak. Boy are they a bear to tighten in the car though.