It starts to studder like its not getting a good gas flow, then it dies.

Have the charging system checked to make sure you are getting 14.25 volts when idle and everything on,blower on high and headlights on .if you are not getting at least 13.60 then replace the alternator,and or out put cable from alternator

it is most likely a faulty injector if it has the throttle body type

Look for a light on the dash that says SECURITY after it doesn't start. These cars and many more GM's have had problems with the antitheft system. Parts in the system tend to fail and cause this "no start" situation. Symptoms range from stalling while driving, to starting for 1-5 seconds and then stalling. This link might help you if this ends up being your problem.
http://vatspasslockpasskeysecurityhelp.yolasite.com/

My 97 Legacy started to studder when stepping on the gas from a dead stop. It does not seem to studder at higher speeds. Do you thing the Fuel filter may need to be changed?

Not to be hurtfull,but, I would not use or listen to jiffy lube or a mechanic that discribes your vehicle issues as -gone. Find and use a good local repair shop. Perferably one with an ASE Certified Tech, that will be looking over your vehicle. Need more info or the vehicle. Could be a timing chain,fuel pump,worn out distributor etc.

I have the same exact problem that just started immediately AFTER I got a tranny service where they changed the Trans Fluid, Trans Filter, Fuel Filter. Took it back and they say nothing is wrong with it. Took it to the dealer thinking I could get some REAL answers... they just told me to replace spark plugs, wiring & coil, for $900. Only studders when quickly accelerating above 40mph. I've check other forums, they say to clean the Mass Air Flow sensor. Haven't tried it yet. This seems the easiest before replacing spark plugs. Any other suggestions anyone?? Please.....

I also agree it sounds like a fuel pump issue. Its easiest to remove the box (6 bolts {need impact wrench} disconnect wires at plugs and disconnect gas filler hose) and lift box up. A hoist is easiest but 6 people can lift it easily. The fuel pump can easily then be replaced. Takes about 1 1/2 hrs. to do entire job this way and its so much easier!
Good Luck!

Defective fuel pump or cloged fuel filter,

First change fuel filter and then change air filter. A turbo requires good air flow to spool-up correctly

need to have the alternator tested sounds like a bad voltage regulator.