my poor car

i have a 99 gs-t and it stalls and sputers and i only get 200 miles to a tank of gass on premium... i have gotten help for a friend he said it was the MAS. i need some help witht his

could be the MAS, it's probably a bad spark issue (replace plugs and wires) or it also sounds like a bad front 02 sensor, which puts your car into safety mode which has the symptoms you described.

Do you have a check engine light, because as crunchy said if it's in safe mode it will run like ass. Not all check engine lights will make it run in safe mode though.