[SubaruCop]

I can tell you that it's probably not the wheel balance. It's the slime causing the shimmy in the tire. I had experience with slime and while it did its job, it caused serious vibration in the front on my hyundai at the time. Many people don't know that shops will not touch tires with slime, some many try to rebalanced the tire, but in my experience they won't even do that. The tire us essentially ruined after slime is installed. The tire will hold up but that's about it. The vibration you are feeling is because the slime moves around in the tire and causes it to be out if balance, even if you rebalanced the tire, keep in mind that slime is a liquid and will constantly move. As the car sits, the slime will collect at the lowest point in the tire and will take a little bit on each drive to distribute it. Hope this helps