How old is your car? If air filter is good, there could be the problem of convertor...If it is close (<100), add some treatment in gas first and see if it works.
-ondway(一枫家新);
2002-2-8(#362953@0)
you may try 爱美人更爱江山& holly's suggestion first, it is free from changing any parts if it works.
-ondway(一枫家新);
2002-2-9{203}(#363346@0)
I am a little afraid the difference for NO is too big. A friend's TOYOTA CORROLA had the similiar situation, he changed convertor finally. but it cost money. Try all ways free from charges first, right?