droping

Hello all, I have a seat Ibiza 2008 1.2 6L. I have had a problem with the idle dropping when on the biting point. Any suggestions as to what this could be? Thank you

right ive had this problem for quite a while now and its starting to do my nut in il try explain whats happning the best i can first of all ive checked for leeks and none found the dv is a forge 007p wich it had a sevice last week with the sevice kit from forge so new o-rings all round...