1995 Volvo 940 Fuel filter or not??

Help, help help! We bought this car new and have kept it in great condition. about a year ago the gas gauge stopped at 1/4 tank. We kept track of how many miles a tank would get us (about 400 miles) In April the car wouldn't start and was towed. We were told it was the fuel filter and that would fix the gauge as well. The fuel filter was put in... 2 days later... it started choking back and eventually stalled. It was almost like out of gas. (The gas gauge was on 1/4 tank empty when this happened .) Dealership had car and stated it had something to do with fuel pump but didn't know what. They had it for several days. Was told to fill the car up with gas and if it continued to choke back and stall out bring back. They swear it's the right fuel pump. We now get 250 miles per tank!! The car stalled out again... It just starts choking back and dies... again it was below 1/2 tank almost 1/4. Tomorrow it gets towed in.......................... They swear they don't know the problem but they are willing to look at it. It is at Saab Shop in Nashville, TN. Any help here. PLEASE........... i don't want to get rid of this car but I'm afraid to drive it and the gas difference is killing me.

Thanks!