I believe am havin da same problem as well...
I hav lexus es300 92, bought it a few months back...nd few weeks ago da engine light came on...I took it to the mechanic nd he told me dat it's air-fuel lean malfunction. I believe dat's cause of the o2 sensor? Am now wonderin shud I buy nd try changin it myself or go to a mechanic nd hav it changed...as i dont kno much bout it.
Also, when i took my car to the mechanic he told me that i shud get the timing belt changed fr my car as it has gone beyond its limit. I was wonderin after how many km shud i change the timing belt?