Mike, as Chris says, a jig saw is not the tool to grab when you want a nice clean, straight cut. It is the tool to grab when you want a curved cut or to rough cut from a hole or other things. Use a table saw or such. BUT, it sounds like your problem is that the saw is not tracking well. Some jig saws do have blade guides, that help, but these are fancier saws. It is not uncommon for jig saws to want to "pull" to one side or another. Even when using a straight edge they wander. If you choose a slower blade, and don't cut too deeply, and feed VERY slowly, you might get a better cut, but it again, is not a saw to cut nice clean straight edges.