I was having uneven tension problems and after I bought the towa gauge, I discovered that the five bobbins that came with my HQ did not turn evenly in the bobbin case. When I pulled, the tension would bounce around about 50 points. Once I stopped using them, that uneven tension problem went away.
BTW - the bobbins I got with the machine were very different than what HQ is selling now. They were quite a bit thicker and heavier.