When i am going up up a hill the car starts to sputter? on 1999 Ford Taurus

When i am going up up a hill the car starts to slow down andd sputter, but it only happens when going up hill what can i do to fix this? will throwing some gas treatment in help?

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2 answers 3 comments
do u have a ck eng liyr on? may have to get tested by mech that can read live data on scanner
i dont have a check engine light on
ck for misfire or plugged exhaust system
po430codewhenhookingituptpcomputer
as said catt issue