96 legacy looses power, why?

I have a 96 legacy GT wagon that has been running fine but now is prone to fits fits of power loss and then the engine dies. Just before this happens the speedometer and tachometer needle drop off and when I try to give it gas it just fizzles into a engine stop.
I had a new battery put in recently and replaced the alternator hoping this would fix the problem but it happened again last night.
If I let the car sit over night I can usually starts it and it stays running for a bit, maybe five-ten minutes then goodbye.
this happened last week (after the new battery and alternator) but I was able to start it and drive it for almost 150 miles before it happened again.
ANY IDEAS?

Have you checked the fuel pressure?
Check the fuel pump and filters as well as the fuel lines for particle debris.

Have you checked the fuel pressure?
Check the fuel pump and filters as well as the fuel lines for particle debris.
That could be it as it does react like it is ot getting enough fuel and gradualy die out. Iwent to my owners manual and it said that the fuel filter should only be changed by the subaru dealer as it is under pressure....
Can I change it myself?

Have you checked the fuel pressure?
Check the fuel pump and filters as well as the fuel lines for particle debris.
That could be it as it does react like it is ot getting enough fuel and gradualy die out. Iwent to my owners manual and it said that the fuel filter should only be changed by the subaru dealer as it is under pressure....
Can I change it myself?

I replaced my fuel filter and pump in my Subaru. Mine was a 91 though. However the only real difference between the early nineties and the late nineties was the body style. The had the same engine, trans driveline, auxillary systems and such. If you are mechanically incline it can be done. In order to replace the filter you have to depressurize the system which is part of the fuel pump replacement process. I had a Haynes manual, which I found to be more useful and accurate than the Chilton's. They have better wiring diagrams too. In the Haynes manual it had the step by step process of replacing the fuel pump and filter. Good luck