96 tacoma 2.7 runs rough and sputter

Hey everyone I just bought a 96 2.7 l that has 131000 miles. When I bought it, it had a check engine light on for p0171 lean fuel mixture on bank one. The truck ran totally fine got it home no problems. I had taken off the battery cable to reset the computer and now it has no light on idles totally fine but when I drive it, it has no power sputters and runs rough. I was wondering what you guys think could be the problem. I have checked the maf and it's clean and the throttle body looks a little dirty but not horrible. The air filter is dirty and will replace it tomorrow to see if it help what would you guys do? The previous owner said that his mechanic said that the computer was messed up but the code is for lean fuel mixture.

 

I'd bet that the catalytic converter is clogged, can cause those symptoms. Also never a bad idea to change spark plugs and wires. Good Luck

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