woosha

I have a friend with a subaru outback 2.5 and it starts and runs but you start to go down the road and step on the gas and it wants to cut out and die. let off the gas and it starts to comeback and run ok. It has new plugs and wires and we tryed a coil pack and that didnt help. the exhast is ok not pluged and no codes. Checked the fuel filter and thats ok. TPS?