Problems with Peugeot 306 xn 1.4 1999

Hello well, I just wanted to see the possibility that someone here guides me about a problem with my car. First, the fault light (K) turns on, sometimes when giving contact lowers the revolutions until it turns off again, this happens at any time of the day, it is not something fixed only sometimes. They have told me that it can be for the injectors, benzine filter, air filter and well an endless arguments that I still do not completely verify.

If there is someone who presents any solution, I will thank you

I would like to get more information about your vehicle, and the light that turns on what color is? It's like (Check Engine).

Have you tried by disconnecting the YAC valve? The slowdown?