mac, can you state how many degrees out , also sounds like impact damage on passenger side ? Don't bang your head to find out out the "elusive why" so much as what can correct it which can be easier than most think.If acceleration pulls right - then probably too much neg. camber on that passenger strut geometry. If pulls right when braking or heavy eng. braking then probably "straight-up", or even pos. camber on pass. geometry.Pulling from camber due to inner vs outer tire contact being "exagerrated"-square tires WORSE.
Tip - camber can be dealt with +- 2 deg. (if non integral strut/spindle) by loosening two strut to spindle bolts and forcing inwards or outwards and then tightening - you got that much leeway (usually).To get more angle deflection - you would "slot" the strut's hole (gotta pick a top or bottom hole) Now you may have 3+ deg. possible play!
What you need is a torpedo level or better yet a "protractor-360 deg." (round) level. held against your wheel ("Mags" may need a wood template to be able to register "vert. angle proper).