There is a mile if threads on this forum on the cheap handling fix - chf. Make the effort to search on this forum. There are comments, instructions and photos - a wealth of info. Virtually all the feedback is positive.
I did mine this Spring, front and back, and it made a big difference with handling. No more having to constantly turn the steering wheel to make corrections.
A far as warranty, fed law requires manufacturers to prove that your mods caused the issue. Ha. If they don't want to honor that how much time/$s are you willing to spend proving the point? In the meantime you are still stuck with your problem. Not suggesting chf is causing a problem!!!