FMQ takes practice and every machine is different. In fact, I think every person is different, too. I have the PQ1500S and I find I want to go too fast when I'm doing FMQ. When I get to speeding along, the thread shreds. A larger needle helped some, but I have to remember to slow down on the curves.
Also, larger quilts want to get hung up on the right front edge of the extension table. Even a bit of a hang up messes up the flow. I have to remind myself to watch out for that, too.
I have never messed with my bobbin tension. That just flat scares me. I'm convinced I will never get it right again if I fiddle with it. As for upper tension, it seems to want to be different for different projects. I just have to play with it to get it right. I use a sample until it looks good.