Ted
Lots of possible fixes.
Is the work anodized prior to welding?
There are lots of threads on this subject here... Try a search of Aluminum GTAW or X-ray and you will find a bunch of info.
Please forgive if this sounds over simple.... Were the indications Bright or Dark... If the indications were bright than the problem is not porosity but scattered tungsten... Just a shot in the dark:) but have seen this mistake before.
Next, your tube should be prepped with abrasive (I like a 120 grit aluminum oxide flapper), this needs to be done just prior to welding or the parts bagged after prep. Remember also to prep the faces of your pipe, any resudual burrs will catch oil etc and bring hydrogen into the picture.
No root gap... faces should be tight.
6061 is also soluable to Hy, the Hydrogen usually escapes as the weld freezes, however if the work is overheated more Hy will dissolve into the weld than can escape and this can be interpreted as fine porosity (usually found in greater quantities near weld terminations) Decreased amps, increased travel speed, increased wire size to cool the puddle or a combination of the three may be effective.
Yeah, in my opinion, Aerowave is no real advantage in the configuration you are describing unless you are trying to really produce high quantity via some form of automation (which Aerowave is not particularly friendly to by the way). Normal settings ought to be just fine.
Also keep in mind that with Aerowave your balence control is a *percentage* up to 90% EP. So when you have your Aerowave set at about 72 it is approximatly equivelant to your synchrowave set to 10 (max penetration) Therefore, when you go past about 75 you will need absolute perfect surface prep and possibly a slight bump in EP amplitude to provide sufficient etch.
If your torch is water cooled, you might consider loosing the thorium and move to a full length 1/16 cerium or zirconium electrode. Neither Cerium or Zirconium tend to spit across the arc plasma or distort at the tip like thorium will when overheated.
You ought to be able to get D17 quality welds in aluminum tubing with no purge.