1998 Subaru Forester Stalls at random, any speed, any time

The car was unused for about 4 weeks. Upon driving it again, it began to stall at random, typically once in a 50 KM trip. The engine slows and seems to lack power. When you put your foot on the gas, the engine balks then dies. Turning off the ignition and restarting is fine. The engine then runs smoothly and I am able to continue driving until it stalls again 5 to 15 minutes later.

The initial engine code was 0304. I R and R'ed that plug but the problem persisted. Since the symptoms appaered fuel system related I have done a number of things diagnosticly and replaced parts.

-new fuel filter: no change
-new fuel pump: no change

There is no smell of gas. The fuel pressure regulator is behaving normally. Fuel system pressure is within tolerences. No codes are shown when the reader is attached when driving. The car starts fine and idles smoothly and at the correct RPM even after warm up.