2003 saab 9-3 engine ligth and loosing power

2003 saab 9-3 My car runs ok on the street,but not on the hyway,when I drive like 15 minutes or more and I get to the street, the engine looses power and set a code for air flow sensor,I replace it ,tps sensor too, the proble continues, some one have any idea what could be, thank you.

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