The 'pod' on top of the pump is a fuel enrichment diaphragm. It limits fuel when you are pulling out to prevent smoke and then uses a vacuum signal to give you more fuel once you are at higher RPM's.
It does sound like you are getting air in your system. Have you done any work to the car lately, fuel filter perhaps. Sometimes a new filter won't always seal up properly. Also look for a puddle under the front of the engine. When the pump drive seal goes bad it can drain the fuel down out of the pump. Check all your fuel line connections and make sure they are tight. Perhaps changing the washers on the banjo bolts would be a good idea. Do you have any fuel around the throttle shaft of the pump? That is another common place I see air getting in. If there is nothing obvious sometimes putting a check valve in the line between the filter and the pump prevents the fuel from being able to drain back into the tank. It is ideal to fix the problem right if possible though, rather than just using a valve as a band-aid.