Your signature line says IO375, so I'm assuming you have a Superior "cold air" manifold. It has a small plenum. The photo below is a standard Lycoming horizontal sump, which has a large plenum. It was taken with a borescope inserted through the throttle body, so the intake tubes are #3 on the left and #4 on the right.
The Lyc horizontal sump incorporates tuned length intake tubes, and as you can see, they sit well above the plenum floor. The tapped hole is the sniffle port. You can see a little bit of fluid there, and a little more in the back of the plenum. This is a tailwheel aircraft, so anything dripping from an intake tube runs to the back.
Point here is that the small plenum Superior sump may vent almost every drop to the sniffle, while a Lyc sump on a tailwheel aircraft can store some volume in its large plenum before much shows at the sniffle. A slight change in leak rate may be very evident with a small plenum manifold. An aircraft equipped with the Lyc sump may be leaking a lot more fuel after shutdown, and not show it.
Photo on the right is looking into the sump plenum with the pipes removed.