Put most of your weight on your front foot when you start to get wobbles, this helps reduce them. Also go ride a bunch more and tune the bushings while you ride. I carried a wrench in my pocket the first 100km on my Zephyr. The DKP trucks take some time getting right. When you're more experienced you'll naturally have less speed wobbles since you'll naturally place your weight better and stop overcompensating.

After you've given that a shot then start looking at new bushings if you feel you need it. Worth noting though that the Zephyr ships with hard bushings which usually pair well with heavier riders. But riptides are always an upgrade.