my father would like to improve the handling and stability of his FXT. it is stock. his main concern is to not effect the warranty. he considers the car to sway to much in cornering, too much lean, and not stable enough at highway speeds.
upon purchase he requested the dealer install the STi rear sway bar. they refused. they also refused to install short throw shifter, although that is a seperate matter.
besides the STi rear sway bar, are there other things he should consider to improve the handling of the vehicle that will not effect the warranty?
btw we have tried varying tire pressure.