Hi my sons 2013 Corsa D 1.4 sri has just had the eml ( emissions ?) light come on. There seems to be no loss of performance just a bit of a lag when dropping back to idle. I have looked up P0171-00 and it seems to be linked to a vacuume leak. I removed the oil filler and it seems to be sucked back on when you re fit it . I also checked the valve outlet on the top of the rocker box but nothing coming out of there. I then took the pcv valve off and can blow through it in both directions. Would i be correct in thinking thats not good ?