@jz,
I think @qwet... wants to buy your car Ultimate Corolla :D.
Today before washing my car, I though to inspect spark plugs and clean air filter and cabin filter. cabin filter was in quite bad condition but for now I cleaned it and reinstall it. Air filter was in good condition even after approx 5k kilometers.
I took few pictures of spark plugs (Denso IK20). If I remember correctly, they were installed at around 12k kilometers so they have been used for 3k kilometers since now.
According to my information, the spark plug color indicates correct air fuel ratio (experts can correct me if I am wrong). Please see the pictures below and provide your feedback about it.







