I'd bet It's comping from the valley pan drain ...

Fuel is very difficult to see, clean it, dry it, feel with your hands.

It's likely return lines or IP seals.

Like I said in the other thread, place a piece of paper under the IP, clean and dry all the injectors and return lines.

Run the motor, then feel for leaks.

If you haven't done the return lines, I would suggest doing them anyways. It fairly cheap to do. Especially if it's hard starting after it's been setting over night.

-Enjoy
fh : )_~