Négative fuel trim
 

Hi!
I m a bit confused, i got a too lean error code for bank 1 and bank 2 .when i look to the fuel trim i saw negative number too get less fuel.which sensor tell what upstream and downstream someone say that it s too rich and the computer take off some fuel.why i get too lean code.
I have installed berk resonated test pipe and custom dual 2.5 inches ss exhaust line what can i do to fix the code
Thank you for your help
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