where should i look first?
System too lean bank 1

 

Generally a system too lean condition is caused by either a dirty MAF sensor (that is not measuring air flow correctly) or a vacuum leak, where unmeasured air (air leaking into the system) is added to measured air, causing the ratio of air to fuel to be off.

First clean the MAF sensor and recheck. After that look for disconnected or cracked vacuum hoses. Especially difficult to find leaks often require the use of smoke to visually find the leak and you might have to hand-off the repair to a good Indie if you don't have such equipment or can't rent it.