I have a Viking MegaQuilter 18x8... which is a rebranded Tin Lizzie.
I agree with PaperPrincess's comments, especially about having an older frame (which me and hubby figured out a deadbar for mine anyway).
Some people have had success using the Towa tension thingy for their bobbin and top tension.
One thing I recommend, is to use dental floss occasionally to clean between the tension disc's on the top. Also, check that your spring-thing (the little flat metal piece) inside your bobbin case is seated correctly. If this gets unseated, it will cause havoc with your bobbin tension. Also, on the top tension, don't be afraid to turn-turn-TURN that knob until you get things "just right".
Those are just some things right off the top of my head. You can PM me with more specific questions, pics, etc if you want to.