I've bought is300, in June check engine light came not long after that, but it was gone for quite a while. Now it happens quite often, and throws cel code bank 1 and bank 2 system too lean. Previous owner put K&N intake. Could it cause the problem, and going back to stock intake is the only solution or should i look for a leak in the hoses leading to it? Thanks

 

vacuum leaks are always possible. oil from the k and n can get on the mass air flow sensor. clean the mass air flow with actual mass air flow cleaner available at most auto parts stores.