This resistor tuning stuff is crap. It simulates colder air and the computer of the car starts to put in more fuel. Bad thing is, that the combustion changes, producing more exhaust gas which will harm your catalytic converter. Please don't do that to your car!!!
I have a nice german text about it. I tranlated it with google, cause I have no time to do it manually. Hopefully it is understandable.
Here it is:
1.) What is made?
A Tuning at the IAT sensor is accomplished.
2.) What makes the IAT sensor?
The IAT sensor measures the temperature of sucked in air.
This is necessary, since the density of air, and thus that are
dependent on the temperature oxygen content.
The IAT sensor is thus important for the air/fuel mixture and the computation of the injected amount of fuel.
3.) What is getunt?
Usually a resistance, is more or less prettily packed wedged between the sensor and the controller.
This resistance changes the measuring voltage, which the sensor sends to the controller in accordance with the Ohm's laws.
4.) What costs this Tuning material?
On the large well-known auction platforms such “Tuningkits” is driven out between 10 and 30 euro. The material equivalent amounts to against it, depending upon source, between few cent and 1 euro.
5.) What happens in the controller and in the engine?
The controller it is vorgegaukelt in this way that sucked in air is colder, than it is actual it. The controller is the opinion that the density of air is higher, and injects more fuel. The mixture, which the engine receives, is thus angefettet. This leads these to FATS so mentioned the burn, supplies indeed minimum more engine performance than the stoichiometric burn in such a way specified. By the other automatic control, which is blocked in modern passenger car, this effect is however strongly minimized.
5.) What are the consequences for the exhaust gas values?
Since the burn is fat now, the output at pollutants partially substantial is increased. With the stöchiometischen burn straight so many oxidizing and reducing pollutants develop that these abreact with one another at the catalyst and the pollutant output of the vehicle is minimized. With the fat burn however increases Carbon monoxide develops (poisonous!) and unburned hydrocarbons remain. The content of nitrogen oxides drops however strongly.
6.) What means for the car?
The following can happen in the consequence. In particular in the short-distance enterprise the entry of fuel is again strengthened in the oil (only Benziner!). The oil loses its functionality faster, it exists a clearly higher danger that the lubricating film tears and a damage to the engine the consequence is. Further the Kat is satisfied permanently with unburned hydrocarbons. This means, which becomes clearly hotter the catalyst, than from the manufacturer intends, and thus can take a damage. At the latest with the next or OUTER ONE after the next, with which a new catalyst is due, this Tuning was no longer cheap. (Catalysts lie between 300 and 1000 euro).
7.) Now there how much Tuningeffekt is?!
As a driver of a car in such a way modified one will probably tighten a better in the lower and middle speed range the vehicle to notice. The maximum performance will not change against it in a larger measure. Also a clear increase of the maximum speed is in my opinion not to be expected.