Use stabilizer. On the Quest, the stitches are up to 8mm, so unless it's stiff/heavy fabric, of course it will tunnel or pucker. Make sure you are threading the pigtail of your bobbin case. If the stitches are forming properly, adjust the balance (a little screw with +/- markings near it). If there's too much top thread showing on the back, tighten the top tension. If there's too much bobbin thread showing, loosen the top tension. Hope that helps.