Just a wild guess by the sound of it. I'm not that au fait with the 3SGTE engine. Mine in a GT4 Turbo, never seems to go wrong, but AFAIK the idle and timing, once it is set, is controlled by the ECU. Presumably the ECU doesn't give any error codes, and I assume you mean you've checked the AFM, rather than the MAF you mention. Or has it been modified?. What model car is it? Mike.