Welding Tips and Tricks

I certified to weld Iso Phase a few years ago and had problems with porosity. One of the other guys testing had very little porosity and I can't figure what was causing it. I almost failed the test. We were using the same machine (Cobra Matic) and the same settings. I had welded Iso Phase befor on a Nuke and never had a problem. Any hints??

If all other aspects of the weld test were the same, including base metal,fit-up,etc..... my only suggestions would be angle of the gun and/or the distance between the nozzle and joint,resulting in insufficient gas coverage......ron