Yes Virginia, there is a Santa Claus!
I got my Spidertax tube in the mail today, and installed it as soon as I got home. I was so amazed by the difference that I made my 20 year old daughter drive it to get an impartial judgement. (She had just driven it before the installation, to run for a gallon of milk.) She agrees, NOTEABLE improvement.
Here in Pittsburgh, we're almost always starting from a dead stop on some pretty steep hills. That UHH-HUHH clutch feathering is totally gone.
The little 1300 now sings a much sweeter song, and her range of notes is devoid of the previous flats and sharps in the midrange.
If you have a carbed 1.3 without this simple fix, by God do it!