Fuel pressure regulator. The big hose (rear) is the fuel return line to the tank. The small hose carries the manifold vacuum to the regulator from a small fitting on the manifold.

The common failure modes cause the engine to run rich -- sometimes so rich it floods and can't be restart. Sometimes so rich fuel washes down the cylinder walls and raises the oil level.

The first failure mode is the small vacuum hose splits, so the regulator thinks the vacuum is low and enriches the mixture.

Another failure mode is the internal mechanism binds (rust?) so the diaphragm stays in the "low vacuum" position -- with the same results.

Yet another mode is a pinhole in the diaphragm so raw fuel is sucked directly into the manifold via the small hose.

Generally you have excessive black exhaust and a smell of gas, along with the typical hard starting and "hunting", or loping idle. Plugs will be black and fouled, wet with gas. Dipstick might read overfull and smell of fuel.

If this happens, an oil and filter change is important.