On the 2/27/10 show that aired on Minnesota Public Radio, a caller said his Saab 900S ran rough when the gas tank got to about 1/2. The problem is common to high mileage Saab 900s.
There are TWO (2) fule pumps in the 900 gas tank. The main Bosch pump is the high pressure pump that provides fuel to the engine. It resides in a bucket at the top of the tank. There is a small, low pressure pump attached to the bottom of the bucket that keeps the bucket full so the main pump always has fuel to keep it cool. That smaller pump is more prone to failure. It is not very expensive, maybe $30-$40.
The listener also commented that it seemed difficult to fill the car at the gas pump. Yes, I have had this problem as well. Just pull the nozzle out a little to allow the tank to breathe and there is no problem filling the tank.