Puffing is definetly the QEV, take it out and reseat it by pushing it all the way in, the pointed bit facing outwards then push the plug in with the little slit matching up to the hole. Reseating an old QEV doesnt always work, but sometimes you get lucky, with the leak i'd just replace orings. Have you checked the mini oring under the noid? That can dislodge after taking the marker apart