04 Escalade Rocks From Side To Side

I recently purchased an 04 Escalade, that initially had rear air suspension, but was converted over by the previous owner to now coil springs. I’m not sure how long before I purchased the vehicle that it was converted over, or even if that matters, but I’ve noticed that the vehicle rocks from side to side tremendously. Ive upgraded all 4 shocks to Extra Heavy Duty, and even made some upgrades to the front and rear sway bar & bushings but the problem stills persists. Does anyone have any idea what this could be?