Makes no sense that rotating tires would fix that unless your tires were never rotated in over 10K miles and cupped, or way too much or too little PSI. I'm betting you probably have stamped steel control arms based off your username 16 silv, and any level kit over 2 inches creates problems with those arms.
Rough country made a kit specifically for these arms now with their 2.5 kit, it uses a preload spacer now for them instead of the bottom and top spacers used in all the other kits over 2 inches. I would install that kit or remove the 1/4 inch spacer from yours, AND make sure your tires are balanced correctly and alignment is correct. If all of the above have been checked, it's most definitely the kit being too much for those stamped arms.
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