1999 Oldsmobile Alero Car Stalls, has trouble starting back

I have a 1999 oldsmobile alero with 151000 miles on it. It's been having trouble starting where it starts up and chugs really bad almost like it's gasping for air and then dies. After several tries I can usually get it to start up by stepping on the gas while I turn the ignition. Once I get moving it will suddenly just die (no chugging or warning) after a mile or so and then I have to go through the whole routine of trying to get it to start again. I took it to a mechanic and they were stumped. They cleaned the throttle but that didn't seem to help.

My thoughts are it's the fuel filter because I haven't changed it in a long long time but the mechanic said they checked the pressure of the fuel system and it all appeared to be okay.

Any thoughts on what this could be?