[77newell]

Additional thought; if the bubbles are present when the engine is running but not when it's stopped AND there is no loss of prime when stopped then the leak is in the filter housing. Besides the gasket, if you have the water collector and drain, the drain could leak under the suction of the fuel pump operating. In the scenario I've noted you would be looking for leaks anywhere downstream of the check valve in the fuel supply line to the filter and upstream from where you are observing them.