Does this only happen when the aircon is on? The following comment is specific to the 2ZZGE, but will apply the 1ZZ as well, imho. The ECU has an integrated idle up function. Via sensors, this function is activated and sends and receives signals from the idle control valve. Now, your idle control valve also controls your idle speed during warm up cycles after a cold start. The aircon compressor fitted to the RunX RSi is a very small unit, which saps a small amount of horsepower, when activated. But saying that, it runs a hefty 12 bar worth of pressure. When the compressor activates, it will put some strain on the engine and rpm would decrease, at idle, from +- 800 rpm to around 500 rpm. The idle up function will communicate with the control valve to up rpm, typically to around 1200 rpm. However, in extreme conditions, like a hot day in traffic where you’re pottering around at walking speed, the activation and deactivation of the compressor, together with the activities of the control valve can result in the symptom described. This is mainly attributable to the fact that there are a variety of factors that could all be applicable at that point in time. Consider that the activation and deactivation of the aircon compressor is dependent on the gas temperature, the gas pressure as well as evaporation radiator activities. This will result in continuous activation and deactivation of the compressor as well as continuous activity from the idle up function to try and compensate for this. The result is “idle hunting”. That’s the long of it. The short of it….its normal and there is no need to be concerned. Here is the link with some background to the South African owner's concerns. http://www.tolken.co.za/twincamforum/viewt...?t=5320&start=0 Hope this helps