Park it!
Sorry, couldn't help myself.
If you haven't already, get it aligned. That alone solved 80% of the handling issues I had with ours. After that, there are myriad options for improving handling - and opinions to support them. What will work best for you is probably unique to you. Some of the options:
- Steering stabilizer
- Upgraded front sway bar
- Upgraded rear sway bar
- Rear track bar
- Upgraded shocks/springs
- Air Bags
If tail-wag really is the problem, then the rear track bar is a good idea as Swyatt suggested, but if the tail is wagging because the front-end is getting pushed around...
Good luck!
Regards,
Randy