I have a Audi 2001 A4 Quattro 1.8L That has a code 17536 which says Long term fuel trim system too lean bank 1. Only modification i have is a k&n air filter and when i put that in i had a code come up saying mass air flow sensor so i took it out and cleaned it in a ziplock bag with denatured alchohol and dried it out and put it back in and code went away and car ran better. Several months later i have this new code pop up with the fuel trim....Anyone have any ideas?

 

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im going for a vacuum leak