Shimmy and floating feeling

I have a 22 Tacoma Sport and I had the 10k service in December. Noticed a shimmy/vibration in the rear over 40mph as well as rear fishtail when taking turns too fast. Took it back in and they couldn’t find anything wrong but had them balance the tires. One rear tire was 12 oz out of balance. They added weights. Still having a very slight shimmy and now it feels floaty like I don’t have as much control especially on the highway. Tire pressures are good. Any idea what is going on? I only have 13k miles. Thanks!!

 

You should probably post this in the 3rd gen forum. This is for 95.5-04 tacomas. You’ll likely get more help over there with your generation.